KR101887534B1 - The method for charging of lithium air battery module - Google Patents

Abstract

A method of charging a lithium air battery is provided. The charging method of the present lithium ion battery includes the steps of charging the lithium ion battery; And discharging the lithium air battery with a current equal to or lower than a reference value.

Description

[0001] The present invention relates to a charging method of a lithium air battery,

The present disclosure relates to a lithium air battery and a charging method for a lithium air battery.

It is known that a lithium air battery has a cathode capable of intercalating / deintercalating lithium ions, a cathode containing oxygen as an anode active material and containing an oxidation-reduction catalyst of oxygen, and a lithium ion conductive medium between the anode and the cathode have.

The theoretical energy density of the lithium air battery is 3000Wh / kg or more, which corresponds to about ten times the energy density of a lithium ion battery. In addition, lithium air cells are environmentally friendly, and many developments are being made to provide improved safety over lithium ion batteries.

In the conventional lithium air battery, polarization is generated due to high overvoltage during charging and discharging, and energy efficiency during charging and discharging is significantly lower than that of a lithium ion battery.

Various catalysts have been used to lower the charge / discharge overvoltage but the charge and discharge overvoltage has not been sufficiently reduced. Therefore, there is a need for a method capable of reducing the charge / discharge overvoltage to improve the charge-discharge energy efficiency.

The present disclosure provides a lithium air battery in which energy efficiency is remarkably improved due to a decrease in charge / discharge overvoltage, and a charging method thereof.

According to one aspect of the present invention, a method of charging a lithium ion battery includes the steps of charging the lithium ion battery; And discharging the lithium air battery with a current equal to or lower than a reference value.

The reference value may be less than or equal to a minimum current when the lithium ion battery discharges through the load.

The charging step may include charging the lithium ion battery until the voltage of the lithium ion battery reaches a reference voltage with a constant current; And charging the lithium ion battery until the voltage of the lithium ion battery reaches a reference voltage until the current of the lithium ion battery reaches a reference current at the reference voltage.

The reference value may be equal to or less than the reference current.

Also, the reference value may be a value between the constant current and the reference current.

The reference value may be 0.5 mA / cm ² or less.

Also, the discharging may discharge the lithium ion battery until the capacity of the lithium ion battery becomes the reference capacity.

The lithium air battery includes a cathode including lithium, a cathode using oxygen as a cathode active material, and an organic electrolyte. The organic electrolyte includes an organic compound capable of absorbing and desorbing electrons involved in an electrochemical reaction can do.

In addition, the organic compound may include a conjugated system.

And, the organic compound may include an aromatic hydrocarbon ring.

In addition, the organic compound may include a quinone compound.

The organic compound may be at least one selected from the group consisting of 1,2-benzoquinone, 1,4-benzoquinone, 1,2-naphthoquinone, 2,3-naphthoquinone, Quinone, 2,3-anthraquinone, 1,4-anthraquinone, 9,10-anthraquinone, 1,2-pyrenedione, 4,5- pyrenedione, 1,2- , 5,6-coronenetetranone, and 1,2,5,6,9,10-choloranil (tetrachloro- p -benzoquinone), Lawson, 2-Hydroxy-1,4 -naphthoquinone, DDQ (2,3-Dichloro-5,6-dicyano-1,4-benzoquinone), tetrafluoro-1,4-benzoquinone, 7,7,8,8-tetracyanoquinodimethane , And 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane.

In addition, the organic electrolyte may include a salt of an alkali metal or an alkaline earth metal.

The negative electrode may include lithium metal, a lithium metal-based alloy, or a lithium intercalating compound.

Further, the anode may include a conductive material.

The conductive material may include a porous carbon-based material.

The disclosed lithium air battery includes an organic compound capable of intercalating and deintercalating electrons involved in an electrochemical reaction of the organic electrolyte, thereby reducing the charging / discharging overvoltage of the lithium air battery and improving energy efficiency.

It is possible to ensure an active interface at the time of discharge by pre-discharging when charging the disclosed lithium ion battery.

FIG. 1 is a view schematically showing a lithium air battery according to an embodiment of the present invention.
2 shows a structure of a lithium ion battery according to another embodiment.
3 is a schematic view of a battery pack including a lithium ion battery according to an embodiment of the present invention.
4 is a flowchart illustrating a charging method of a battery pack including a lithium ion battery according to an embodiment of the present invention.
5 shows the result of measuring the voltage gain in the absence of the pre-discharge.
FIG. 6 shows the result of measuring the voltage gain when there is a pre-discharge.

Hereinafter, the disclosed lithium air battery will be described in detail with reference to the accompanying drawings. In the following drawings, like reference numerals refer to like elements, and the size of each element in the drawings may be exaggerated for clarity and convenience of explanation.

As used herein, the term "air" is not meant to be limited to atmospheric air, but may include a combination of gases containing oxygen, or pure oxygen gas. This broad definition of the term "air" can be applied to all applications, such as air cells, air bubbles, and the like.

FIG. 1 is a diagram schematically showing a lithium-ion battery 10 according to an embodiment of the present invention. 1, a lithium air battery 10 includes a positive electrode 11 containing oxygen in the air as a positive electrode active material and containing a redox catalyst of oxygen, a negative electrode 12 capable of storing and releasing lithium ions, And a first electrolyte 13, which is a lithium ion conductive medium, between the cathode 11 and the cathode 12.

The anode 11 is formed on a first current collector (not shown), and oxygen is used as an active material. The cathode 12 is formed on a second current collector (not shown) and is capable of storing / emitting lithium. As the current collector, it is possible to use a porous body such as a mesh or mesh in order to accelerate the diffusion of oxygen, and a porous metal plate such as stainless steel, nickel, or aluminum can be used. However, the present invention is not limited thereto. Anything that can be used is possible. The current collector may be coated with an oxidation-resistant metal or alloy coating to prevent oxide.

On the other hand, as the anode 11 using oxygen as a cathode active material, a conductive material can be used. The conductive material may be porous. Therefore, any material having the above-mentioned porosity and conductivity can be used as the positive electrode active material without limitation, and for example, a carbon-based material having porosity can be used. Examples of such carbon-based materials include carbon blacks, graphites, graphenes, activated carbons, and carbon fibers. As the cathode active material, a metal conductive material such as a metal fiber or a metal mesh may be used. Further, as the cathode active material, a metallic powder such as copper, silver, nickel, or aluminum may be used. Polyphenylene derivatives, and the like can be used. The conductive materials may be used alone or in combination.

A catalyst for oxidation / reduction of oxygen may be added to the anode 11. Examples of the catalyst include noble metal catalysts such as platinum, gold, silver, palladium, ruthenium, rhodium and osmium, manganese oxides, Oxides, nickel oxides, and the like, or organometallic catalysts such as cobalt phthalocyanine may be used, but the present invention is not limited thereto, and any catalyst that can be used as an oxidation / reduction catalyst for oxygen in the art can be used.

In addition, the catalyst may be supported on a carrier. The carrier may be an oxide, zeolite, clay minerals, carbon, or the like. The oxide may include one or more oxides such as alumina, silica, zirconium oxide, and titanium dioxide. Or an oxide comprising at least one metal selected from Ce, Pr, Sm, Eu, Tb, Tm, Yb, Sb, Bi, V, Cr, Mn, Fe, Co, Ni, Cu, . The carbon may be carbon black such as Ketjen black, acetylene black, tan black, lamp black, graphite such as natural graphite, artificial graphite and expanded graphite, activated carbon, carbon fiber and the like, Anything that can be used as a carrier in the field is possible.

The anode 11 may further include a binder. The binder may include a thermoplastic resin or a thermosetting resin. For example, it is possible to use polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene-butadiene rubber, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, vinylidene fluoride- Vinylidene fluoride-fluorotetrafluoroethylene copolymers, vinylidene fluoride-chlorotrifluoroethylene copolymers, ethylene-tetrafluoroethylene copolymers, polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene lower copolymer, propylene-tetrafluoroethylene Ethylene-chlorotrifluoroethylene copolymers, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymers, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymers, ethylene -Acrylic acid copolymer, and the like can be used alone or in combination, but the present invention is not limited thereto. Anything that can be used as a binder in the technical field is possible.

For example, the anode 11 may be prepared by mixing the oxygen oxidation / reduction catalyst, the conductive material, and the binder, and then adding a suitable solvent to prepare a cathode slurry, applying and drying the anode slurry, For example, by compression molding on the current collector. In addition, the anode 11 may optionally include lithium oxide. Alternatively, the oxygen oxidation / reduction catalyst may be optionally omitted.

The anode 12 capable of intercalating and deintercalating lithium includes a lithium metal, a lithium-metal-based alloy, or a material capable of intercalating and deintercalating Li, but the present invention is not limited thereto. The cathode 12 determines the capacity of the lithium-ion battery 10. The lithium metal-based alloy may be, for example, aluminum, tin, magnesium, indium, calcium, germanium, antimony, bismuth,

The second electrolytes (25) and (13) may be an aqueous electrolyte or a non-aqueous electrolyte. Or the second electrolytes 25 and 13 may be formed by mixing the aqueous electrolyte and the non-aqueous electrolyte. In the case where the second electrolytes (25) and (13) are aqueous electrolytes, the following reaction scheme is shown.

[Reaction Scheme 1]

4Li + O ₂ + 2H ₂ O -> 4LiOH E ^o = 3.45 V

And,

When the second electrolyte (25) (13) is a non-aqueous electrolyte, the reaction mechanism as shown in the following reaction formula (2) can be shown.

[Reaction Scheme 2]

4Li + O ₂ ↔ 2Li ₂ O E ^o = 2.91V

2Li + O ₂ ↔ Li ₂ O ₂ E ^o = 3.10 V

The non-aqueous electrolyte may include an aprotic solvent. As the aprotic solvent, for example, a carbonate-based, ester-based, ether-based, ketone-based, amine-based or phosphine-based solvent may be used.

Examples of the aprotic solvent include nitriles such as R-CN (R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond aromatic ring or an ether bond) , Amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, sulfolanes, and the like.

As the aprotic solvent, each solvent may be used alone or in combination of two or more solvents.

In addition, the non-aqueous electrolyte may include an ionic liquid. Examples of the ionic liquid include linear or branched substituted or unsubstituted ammonium, imidazolium, pyrrolidinium, piperidinium cations and PF ₆ ^- , BF ₄ ^- , CF ₃ SO ₃ ^- , (CF ₃ SO ^{_{2) 2 N -, (C}} 2 F 5 SO 2) 2 N -, (CN) 2 N - may be used are compounds composed of an anion, such as.

The non-aqueous electrolyte may comprise a salt of an alkali metal and / or an alkaline earth metal. The salt of the alkali metal and / or alkaline earth metal is dissolved in an organic solvent and can act as a source of alkali metal and / or alkaline earth metal ions in the cell 10. The salt of the alkali metal and / or alkaline earth metal may serve to promote the movement of alkali metal and / or alkaline earth metal ions between the anode 11 and the cathode 12, for example.

The salt anion contained in the non-aqueous electrolyte is _{^{PF 6 -, BF 4 -,}} SbF 6 -, AsF 6 -, C 4 F 9 SO 3 -, ClO 4 -, AlO 2 -, AlCl 4 -, C x F _{2x +1} SO ₃ ^- (where, x is a natural _{number), (C x F 2x +} 1 SO 2) (C y F 2y + 1 SO 2) N - ( wherein, x and y are natural numbers), and A halide, and a halide.

2 shows a structure of a lithium ion battery 20 according to another embodiment.

A first electrolyte 13 disposed between the anode 11 and the cathode 12; a first electrolyte 13 disposed between the cathode 11 and the cathode 12; A protective film 24 disposed between the protective film 24 and the cathode 12 and a second electrolyte 25 disposed between the protective film 24 and the cathode 12. In FIG. 2, the cathode 12, the second electrolyte 25, and the protective film 24 may be referred to as protective cathodes. Since the anode 11, the cathode 12 and the first electrolyte 13 shown in FIG. 2 correspond to the anode 11, the cathode 12 and the first electrolyte 13 shown in FIG. 1, It is omitted.

The second electrolyte 25 may be a non-aqueous electrolyte.

The protective film 24 is at least one selected from an inorganic solid electrolyte membrane, a polymer solid electrolyte membrane, a gel-type polymer electrolyte, and a lithium ion conductive solid electrolyte membrane.

The inorganic solid electrolyte membrane may be, for example, Cu ₃ N, Li ₃ N, or LiPON.

Examples of the polymer solid electrolyte membrane include a polyethylene oxide membrane and the like.

The polymer solid electrolyte membrane can be prepared, for example, by mixing a lithium ion conductive polymer and a lithium salt.

The lithium salt may be LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiN (SO ₂ C ₂ F ₅ ) ₂ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiClO ₄ , LiAlO _{2 , LiAlCl 4, LiN (C x} F 2x +1 SO 2) (C y F 2y +1 SO 2) ( where, x and y are natural numbers), LiF, LiBr, LiCl, LiI , and LiB (C ₂ O ₄ ) ₂ (lithium bis (oxalato) borate (LiBOB)) may be used.

As the lithium ion conductive polymer, polyethylene oxide, polyacrylonitrile, polyester, or the like is used.

The lithium ion conductive solid electrolyte membrane may include at least one selected from the group consisting of an inorganic substance and a polymer solid electrolyte component.

 The lithium ion conductive solid electrolyte membrane may be a glass-ceramic solid electrolyte or a laminated structure of a glass-ceramic solid electrolyte and a polymer solid electrolyte. The lithium ion conductive solid electrolyte membrane will be described in more detail as follows.

Examples of the lithium ion conductive solid electrolyte film include inorganic materials containing lithium ion conductive glass, lithium ion conductive crystals (ceramics or glass-ceramics), or mixtures thereof. In consideration of chemical stability, the lithium ion conductive solid electrolyte membrane may be exemplified by an oxide.

When the lithium ion conductive solid electrolyte membrane contains a large amount of lithium ion conductive crystals, a high ion conductivity is obtained. For example, lithium ion conductive crystals may be added to the solid electrolyte membrane in an amount of, for example, 50 wt% or more and 55 wt% By weight or more, or 55% by weight or more.

Examples of the lithium ion conductive crystals include crystals having a perovskite structure having lithium ion conductivity such as Li ₃ N, LISICON, La _{0 .55} Li _{0 .35} TiO ₃ , LiTi ₂ having a NASICON structure P ₃ O ₁₂ , or glass-ceramics for precipitating these crystals.

As the lithium ion conductive crystal, for example, Li _{1 + x + y} (Al, Ga) _x (Ti, Ge) _2-x Si _y P _{3 -y} O ₁₂ 1, for example, 0? X? 0.4, 0? Y? 0.6, or 0.1? X? 0.3 and 0.1 0? Y? 0.4). When the crystal is a crystal containing no crystal grain boundary which inhibits ion conduction, it is glass in terms of conductivity. For example, since glass-ceramics have few pores or grain boundaries that interfere with ion conduction, they can have high ionic conductivity and excellent chemical stability.

Examples of the lithium ion conductive glass-ceramics include lithium-aluminum-germanium-phosphate (LAGP), lithium-aluminum-titanium-phosphate (LATP), and lithium- aluminum- titanium-silicon- phosphate have.

For example, when the mother glass has a composition of Li ₂ O-Al ₂ O ₃ -TiO ₂ -SiO ₂ -P ₂ O ₅ and the mother glass is crystallized by heat treatment, the main crystal phase is Li _{1 + x + y} Al _x Ti _{2 - x} Si _y P _{3 - y} O ₁₂ (0? x? 1, 0? y? 1), where x and y are, for example, 0? x? 0.4 or 0? y ? 0.6. x and y are specifically 0.1? x? 0.3 and 0.1? y? 0.4.

Here, the pores or grain boundaries that interfere with ion conduction are meant to mean that the conductivity of the entire inorganic material including lithium ion conductive crystals is reduced to 1/10 or less of the conductivity of the lithium ion conductive crystals in the inorganic material Or an ionic conductivity inhibitor such as a grain boundary system.

The glass-ceramics is a material obtained by crystallizing a crystal phase in a glass phase by heat-treating the glass, and is also referred to as a material comprising an amorphous solid and a crystal. In addition, a material in which all phases of the glass phase are phase- And a material having a crystal amount (crystallinity) of 100% by weight. Even in the case of a 100% crystallized material, in the case of glass-ceramics, there is almost no pores in crystal grains or crystals.

Since the lithium ion conductive solid electrolyte film contains a large amount of the glass ceramic, a high ion conductivity can be obtained. Therefore, the lithium ion conductive solid electrolyte film can contain 80 wt% or more of lithium ion conductive glass ceramics, In order to obtain the conductivity, the lithium ion conductive glass ceramic may be contained in an amount of 85 wt% or more or 90 wt% or more.

The lithium ion conductive solid electrolyte membrane may further include a polymeric solid electrolyte component in addition to the glass-ceramic component. Such a polymer solid electrolyte is a lithium salt-doped polyethylene oxide. Examples of the lithium salt include LiN (SO ₂ CF ₂ CF ₃ ) ₂ , LiBF ₄ , LiPF ₆ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , such as _{LiN (SO 2 CF 3) 2} , LiN (SO 2 C 2 F 5) 2, LiC (SO 2 CF 3) 3, LiN (SO 3 CF 3) 2, LiC 4 F 9 SO 3, LiAlCl 4 For example.

The polymer solid electrolyte membrane may form a laminate structure with the glass-ceramics, and the glass-ceramic may be interposed between the first polymer solid electrolyte containing the component and the second polymer solid electrolyte.

The lithium ion conductive solid electrolyte film can be used as a single layer or a multilayer film.

The operation principle of the lithium ion battery 10 (20) is as follows. At the time of discharging, lithium derived from the cathode 12 meets oxygen introduced from the anode 11 to produce lithium oxide and oxygen is reduced (ORR). On the contrary, lithium oxide is reduced during charging and oxygen is oxidized (oxygen evolution reaction: OER).

On the other hand, even after the lithium air cells 10 and 20 are charged, the undifferentiated Li ₂ O ₂ or electrolytic decomposition products surround the catalytic or electrochemically active interface of the anode 11. Thus forming an overvoltage at the next discharge.

Therefore, by adding an organic compound to the electrolyte, the lithium air cells 10 and 20 according to the embodiment can increase capacity and reduce charge / discharge polarization (= charge voltage-discharge voltage).

The reaction area of the electrode reaction can be expanded by the interfacial reaction between the electrode and the organic compound and the interfacial reaction between the organic compound and Li ₂ O ₂ by the participation of the organic compound in the organic electrolyte in the electrode reaction.

Further, since the property of the interface is changed, the interface resistance is also changed. Therefore, it is possible to remarkably increase the electrode reaction rate, that is, reversible electrode reaction, compared with the conventional lithium air cells, and the overvoltage at the time of charging and discharging can be remarkably reduced.

The organic compound is capable of occluding and releasing electrons involved in an electrochemical reaction and forming an oxidation-reduction couple by oxidation and reduction reactions accompanying the occlusion and release of the electrons. That is, it can participate in the electron transfer of the electrode reaction while alternately repeating the oxidized state and the reduced state.

The organic compound and the organic electrolyte containing the organic compound may act as a mediator that partially or wholly mediates electron transfer between the anode 11 and the lithium oxide during the discharge process. The lithium oxide may be Li ₂ O, Li ₂ O _2, or the like. In this specification, lithium oxide refers to all kinds of lithium oxides including lithium peroxide.

The reduction potential of the organic compound is 2.5 to 3.5 V relative to the lithium metal, and may be included in the charge / discharge voltage range of the lithium air cells 10 and 20. That is, during the discharge process of the lithium air cells 10 and 20, the reduction and oxidation of the organic compound may occur. If the organic compound has a reduction potential in the charge / discharge voltage range of the lithium air cells 10 and 20, for example, within a voltage range of 2.5 to 3.5 V relative to the lithium metal, and maintains a stable state in the organic electrolyte, It can be used regardless of its chemical structure.

Hereinafter, the mechanism of the organic compound and the organic electrolyte including the organic compound involved in the electron transfer in the charging and discharging process will be described in more detail. However, the scope of the present invention is limited only by the scope of the present invention. It is not intended to be.

For example, in the discharge process of the lithium air cells 10 and 20, the organic compound receives electrons from the cathode 11 at a lower voltage than lithium oxide, and is reduced first. Then, the reduced organic compound transfers electrons to oxygen molecules dissolved in the electrolyte and the primary lithium oxide, and is oxidized and regenerated as the original organic compound. The oxygen molecule and the lithium oxide that have received electrons from the reduced organic compound become an oxygen reduction product or a secondary lithium oxide. Then, the regenerated organic compound receives electrons from the anode 11 and is reduced again. By mediating the electron transfer, the distance of the oxygen supplied from the air and the generated primary lithium oxide to the electrode is reduced, so that the average discharge voltage at the time of discharge can be increased.

In addition, the organic compound may stabilize the interface of the lithium oxide through an interaction that is weakly coordinated to the surface of the lithium oxide such as Li ₂ O ₂ . For example, the terminal oxygen of 1,4-benzoquinone or the terminal cyano group of 7,7,8,8-tetracyanoquinodimethane can be weakly coordinated to the lithium of Li ₂ O ₂ . As described above, since the interface of the lithium oxide is stable, the average charging voltage at the time of charging can be reduced.

The organic compound may include a double bond and / or a triple bond in the molecule. The double bond may include a double bond between carbon and carbon, a double bond between carbon and oxygen, a double bond between nitrogen and nitrogen, and the triple bond may include a triple bond between carbon and nitrogen However, it is not necessarily limited to such a range, and any double bond and / or triple bond that can be used in the technical field is possible.

In addition, the organic compound may include a conjugated system. The conjugated structure means a system in which p-orbital is successively connected and overlapped by having a double bond and a single bond alternately connected or having contiguous atoms available for p-orbitals. The conjugated structure is a structure capable of deolocalization of electrons. The delignification of the - electron stabilizes a compound containing a conjugated structure. Therefore, the complex containing the ligand containing the conjugated structure can maintain a stable state upon oxidation and / or reduction. For example, benzene, thiophene, and the like.

The organic compound may include a quinone-based compound. The quinone compounds include quinone and quinone derivatives.

The term "derivative " means that one or more substituents are connected to the above-listed compounds, -Cl; -Br; -CN; -NO2-OH; A C1-C60 alkyl group unsubstituted or substituted with -F, -Cl, -Br, -CN, -NO2 or -OH or a C1-C60 alkyl group, -F, -Cl, -Br, -CN, -NO2 C60 cycloalkyl group unsubstituted or substituted with -OH or a C2-C60 heterocycloalkyl group unsubstituted or substituted with a C1-C60 alkyl group, -F, -Cl, -Br, -CN, -NO2 or -OH, A C5-C60 aryl group substituted with an alkyl group, -F, -Cl, -Br, -CN, -NO2 or -OH and an unsubstituted or C1-C60 alkyl group, -F, -Cl, -Br, -CN, -NO2 Or a C2-C60 heteroaryl group substituted with -OH.

The aryl group is a monovalent group having an aromatic ring system, and may include two or more ring systems, and the two or more ring systems may exist in a bonded or fused form to each other. The heteroaryl group refers to a group in which at least one of the aryl groups is substituted with at least one member selected from the group consisting of N, O, S, and P. Meanwhile, the cycloalkyl group refers to an alkyl group having a ring system, and the heterocycloalkyl group refers to a group in which at least one carbon in the cycloalkyl group is substituted with at least one member selected from the group consisting of N, O, S and P. The fused aromatic ring or the fused heteroaromatic ring is fused to the basic ring and may include two or more ring systems, and the two or more ring systems may exist in a bonded or fused form to each other. And the heteroaromatic ring refers to a ring in which at least one of the aromatic rings is substituted with at least one member selected from the group consisting of N, O, S and P.

Or the lithium air cells 10 and 20 may be charged to perform a slight discharge to activate the interfacial reaction of the undifferentiated Li ₂ O ₂ or the electrolytic decomposition product.

3 is a schematic diagram of a battery pack 100 including a lithium ion battery according to an embodiment of the present invention.

3, a battery pack 100 according to an embodiment of the present invention includes a battery 110 including at least one lithium ion battery 10 or 20 capable of charging and discharging, An external terminal P + and P- for electrically connecting an external power supply or a load, a controller 120 for controlling charging and discharging of the battery unit 110 according to the charged state of the battery unit 110, A charge / discharge control unit 130 for receiving a signal from the charge / discharge control unit 130 and controlling an electrical connection between the charge unit 110 and the external terminals P + and P- The electric connection between the battery 110 and the external terminals P + and P- is provided on the large current path of the battery 110 in order to prevent an overcurrent from flowing to the battery 110. [ And a discharging unit 150 for discharging the battery unit 110 with a specific current.

The battery 110 may include at least one lithium air battery 10 (20) shown in FIG. 1 or FIG. When there are a plurality of lithium air cells 10, they may be connected in series, in parallel, or in series and parallel.

The control unit 120 measures the voltage of the charge unit 110 when the external power supply unit is electrically connected to the external terminals P + and P-. When the measured voltage is lower than the full charge voltage, the charge unit 110 is charged And controls the components of the battery pack such that the battery unit 110 is discharged when the load is electrically connected to the external terminal.

The charge / discharge controller 130 may include a charge FET device (not shown) and a discharge FET device (not shown). Depending on the control of the control unit 120, either the charging FET device or the discharging FET device is driven to charge or discharge the battery unit 110. For example, when the charge section 110 is charged, the charge FET element is driven, and when the charge section 110 is discharged, the discharge FET element can be driven.

The external terminals P + and P- are connected in parallel with the battery 110 and are composed of a positive terminal P + and a negative terminal P-. The external terminals P + and P- electrically connect the battery unit 110 to an external power source or a load so that the battery unit 110 can perform charging or discharging. More specifically, when the external power supply unit is connected to the external terminals P + and P-, the charge unit 110 performs charging, and when a load is connected to the external terminals P + and P- The charge section 110 performs discharging.

4 is a flowchart illustrating a charging method of a battery pack 100 including a lithium ion battery according to an embodiment of the present invention.

Referring to FIG. 4, when the external power source is connected to the external terminals P + and P-, the controller 120 charges the power source unit 110 in a constant current mode. For example, the voltage applied to the battery unit 110 is gradually or gradually increased to apply a constant current to the battery unit 110. When the applied voltage of the battery 110 reaches the reference voltage, the controller 120 maintains the voltage applied to the battery 110 at the reference voltage, until the current applied to the battery 110 reaches the reference current Thereby gradually or locally decreasing the current applied to the charge section 110. Thus, when the current applied to the charge section 110 becomes the reference current, the controller 120 discharges the charge section 110.

The controller 120 can discharge the battery unit 110 with a current equal to or lower than the reference value at the time of discharging the battery unit 110. [ The current below the reference value may be a constant current. The current below the reference value is referred to as a discharge current. The discharge current may be less than or equal to the constant current when charging the battery 110 or less than the reference current. Or the discharge current may be a value between the constant current and the reference current when charging the battery section 110. [ Or the discharge current may be less than or equal to the minimum current when the battery pack is discharged in the state of being connected to the load. For example, the discharge current may be 0.5 mA / cm ² or less.

Here, the discharging current may be performed in a state where the external power source is connected to the external terminals P + and P-. That is, when the current applied to the charge section 110 reaches the reference current, the controller 120 stops driving the charge FET device and drives the discharge FET device. The discharge FET element discharges the current of the charge section 110 to the discharge section so that the charge section 110 is discharged. The discharge in a state in which no load is connected to the external terminals P + and P- is referred to as pre-discharge.

The discharging to the discharging current is performed until the charging capacity of the battery unit 110 becomes the reference capacity. Here, the reference capacity may be 99% to 90% of the charge capacity of the full charge when the battery 110 is fully charged. Or discharging to the discharging current for a certain period of time.

When the current applied to the battery unit 110 becomes the reference current, the battery unit 110 is discharged by the discharge current, thereby removing Li ₂ O ₂ , LiO _2, or an attached substance attached to the active interface of the lithium- It is possible to prevent the overvoltage of the battery unit 110 during the discharge.

The present invention will be described in more detail by way of the following examples and comparative examples. However, the examples are for illustrating the present invention, and the scope of the present invention is not limited thereto.

 (Preparation of organic electrolyte)

Example 1

An organic electrolyte was prepared in which 1 M of Li (CF 3 SO 2) 2N (lithium bis (trifluoromethylsulphonyl) amine, LiTFSI) and 10 mM of 1,2-benzoquinone were added to tetramethylene glycol dimethyl ether (TEGDME).

Comparative Example 1

An organic electrolyte in which 1 M of Li (CF 3 SO 2) 2 N (lithium bis (trifluoromethylsulphonyl) amine, LiTFSI) was dissolved in tetramethylene glycol dimethyl ether (TEGDME) was prepared.

Evaluation Example 1: Evaluation of charge / discharge characteristics

A lithium air cell including the electrolyte prepared in Example 1 and Comparative Example 1 was discharged at 2 mA (vs. Li) at a constant current of 1 mA / cm < 2 > at 60 DEG C and 1 atm, and then charged to 4.7 V with the same current. The insecticidal capacity efficiency at the time of charging / discharging is defined by the following equation (1).

&Quot; (1) "

Insecticide capacity efficiency [%] = [charge capacity] / [discharge capacity] × 100

In the above equation, the charging capacity is the charging capacity at the 4.7V cut-off voltage at the time of charging, and the discharging capacity is the discharging capacity at the 2.0V cut-off voltage at the time of discharging.

As a result, the insecticidal capacity efficiency and the discharge voltage of Example 1 were 42% and 2.32 V, respectively, and the insecticidal capacity efficiency and the discharge voltage of Comparative Example 1 were 16% and 2.17 V, respectively. Thus, it can be seen that the insect repellent capacity efficiency and the discharge voltage are remarkably improved.

Next, the performance of the lithium-ion secondary battery according to the presence or absence of the discharge after charging is examined.

A 1M LiTFSI tetraglyme solution was prepared to prepare a lithium air cell containing the first electrolyte. In Example 2, the lithium air cell is discharged to 1.7 V (vs. Li) at a constant current of 1 mA / cm ² at 60 ° C and 1 atm. And thereby it was charged again at 4.2 V after charging to 4.2 V with a constant current of 1mA / cm ² with a constant voltage up to 0.2 mA / cm ² and then discharged at 0.2mA / cm ^2. On the other hand, Comparative Example 2 discharges the lithium air battery to 1.7 V (vs. Li) at a constant current of 1 mA / cm ² at 60 ° C and 1 atm. Then, a discharge of 0.2 mA / cm < ² > is not performed although only a charge of 4.2 V is performed at a constant current of 1 mA / cm < ² >. This charge / discharge was repeatedly performed.

FIG. 5 shows the result of measuring the voltage gain in the absence of the pre-discharge, and FIG. 6 shows the result of measuring the voltage gain in the presence of the pre-discharge. As shown in FIG. 5, in Comparative Example 2 in which there was no pre-discharge, the voltage gain was decreased as the number of charging / discharging was increased. However, as shown in Fig. 6, in the second embodiment having the pre-discharge, the voltage gain was maintained at 2V or more even when the number of charging / discharging was increased and the voltage gain was decreased.

10, 20: Lithium air battery cell
11: anode 12: cathode
13: first electrolyte 24: protective film
25: Second electrolyte 100: Battery pack
110: electrical part 120:
130: charge / discharge control unit 140:
150: discharge

Claims (16)

In a charging method of a lithium air battery,
Charging the lithium air battery; And
And discharging the lithium ion battery with a current equal to or lower than a reference value to remove a substance attached to the active interface of the lithium ion battery. The method according to claim 1,
Wherein the reference value is equal to or less than a minimum current when the lithium ion battery discharges through a load. The method according to claim 1,
The step of charging comprises:
Charging the lithium ion battery until a voltage of the lithium ion battery reaches a reference voltage with a constant current; And
And charging the lithium-air battery until the voltage of the lithium-ion battery reaches a reference voltage, until the current of the lithium-ion battery reaches a reference current at the reference voltage. The method of claim 3,
Wherein the reference value is equal to or less than the reference current. The method of claim 3,
Wherein the reference value is a value between the constant current and the reference current. The method according to claim 1,
Wherein the reference value is 0.5 mA / cm ² or less. The method according to claim 1,
The discharge may include,
And discharging the lithium ion battery until the capacity of the lithium ion battery reaches a reference capacity. The method according to claim 1,
In the lithium air battery,
An anode including lithium, a cathode using oxygen as a cathode active material, and an organic electrolyte,
Wherein the organic electrolyte includes an organic compound capable of intercalating and deintercalating electrons involved in an electrochemical reaction. 9. The method of claim 8,
Wherein the organic compound comprises a conjugated system. 9. The method of claim 8,
Wherein the organic compound comprises an aromatic hydrocarbon ring. 9. The method of claim 8,
Wherein the organic compound comprises a quinone-based compound. 9. The method of claim 8,
The organic compound may be selected from the group consisting of 1,2-benzoquinone, 1,4-benzoquinone, 1,2-naphthoquinone, 2,3-naphthoquinone, 1,4-naphthoquinone, , 3-anthraquinone, 1,4-anthraquinone, 9,10-anthraquinone, 1,2-pyrenedione, 4,5- pyrenedione, 1,2- 6-coronenetetranone, and 1,2,5,6,9,10-choloranil (tetrachloro- p -benzoquinone), Lawsone (2-Hydroxy-1,4- naphthoquinone) , DDQ (2,3-Dichloro-5,6-dicyano-1,4-benzoquinone), tetrafluoro-1,4-benzoquinone, 7,7,8,8-tetracyanoquinodimethane, and 2 , 3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane, and the like. 9. The method of claim 8,
Wherein the organic electrolyte comprises a salt of an alkali metal or an alkaline earth metal. 9. The method of claim 8,
Wherein the negative electrode comprises a lithium metal, a lithium metal based alloy, or a lithium intercalating compound. 9. The method of claim 8,
Wherein the positive electrode comprises a conductive material. 16. The method of claim 15,
Wherein the conductive material comprises a porous carbon-based material.

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