KR101511792B1 - Additives of electrode active materials for enhancement of battery capacity - Google Patents

Abstract

The present invention relates to (1) a cell performance improving method comprising a polyoxometallate which itself undergoes a redox reaction, (2) an electrode active material additive for improving ionic conductivity in an electrode active material of a battery, and ) ≪ / RTI > to a lithium ion battery comprising such an electrode mixture.

Specifically, the present invention relates to a method for improving battery performance and an additive for the same, characterized in that the electrode active material includes a polyoxometallate which improves the ionic conductivity of the electrode active material and undergoes a redox reaction (oxidation-reduction reaction) .

Electrode, additive, ion, conductive, olivine, reversible

Description

TECHNICAL FIELD [0001] The present invention relates to a method for improving cell performance and an electrode active material additive,

The present invention relates to (1) a cell performance improving method comprising a polyoxometallate which itself undergoes a redox reaction, (2) an electrode active material additive for improving ionic conductivity in an electrode active material of a battery, and ) ≪ / RTI > to a lithium ion battery comprising such an electrode mixture.

BACKGROUND OF THE INVENTION Rechargeable batteries, such as lithium ion rechargeable batteries, are widely used as power sources for battery-powered portable electronic devices such as cell phones, portable computers, camcorders, digital cameras, PDAs, and the like.

As the negative electrode active material, metal lithium, a lithium alloy (for example, a Li-Al alloy), a conductive high molecular material (for example, polyacetylene or polypyrrole) doped with lithium, an intercalation compound inter-layer compounds or carbon materials are commonly used. As the electrolytic solution, a solution obtained by dissolving a lithium salt in an aprotic organic solvent is used.

As the positive electrode active material, a metal oxide or a metal sulfide or a polymer (for example, TiS ₂ , MoS ₂ , NbSe ₂ or V ₂ O ₅ ) is used. The discharge reaction of the nonaqueous electrolyte secondary battery using such a material proceeds in such a manner that lithium ions are eluted into the electrolyte solution at the cathode while lithium ions are intercalated between the layers of the positive electrode active material at the anode. At the time of charging, the above reaction proceeds inversely, and lithium is intercalated at the anode. That is, the charging / discharging reaction is repeatedly performed by repeating the reaction in which the lithium ions from the cathode are introduced into the cathode active material and discharged therefrom.

At present, LiCoO ₂ , LiNiO ₂ and LiMn ₂ O ₄ having high energy density and high voltage are used as a positive electrode active material of a lithium ion secondary battery, for example.

On the other hand, it has been proposed to use LiFePO ₄ having an olivine structure as a cathode active material of a lithium ion secondary battery. LiFePO ₄ has a high bulk density of 3.6 g / cm 3 and can generate a high potential of 3.4 V and the theoretical capacity is as high as 170 mAh / g. In addition, LiFePO ₄ contains Li atoms capable of being electrochemically undoped in an initial state at a ratio of one Li atom per Fe atom, and thus is a material expected as a positive electrode active material of a lithium ion secondary battery. Moreover, LiFePO ₄ is more affordable than LiCoO ₂ , LiNiO ₂ or LiMn ₂ O ₄ mentioned above, because it contains iron, which is a cheap and abundant material as a natural resource, but is more environmentally friendly due to its lower toxicity.

However, LiFePO ₄ is low because the electron conductivity, in the case of using up the LiFePO ₄ as the positive electrode active material, should be added to the conductive material in the positive electrode active material. At this time, the particle size of the conductive material is larger than the particle size of LiFePO _4, the reduced ratio of LiFePO ₄ in the cathode active material becomes less battery power.

Accordingly, an object of the present invention is to provide an electrode active material having an excellent ion conductivity. To this end, the present invention provides an additive for an electrode active material.

It is still another object of the present invention to provide a lithium secondary battery having improved capacity and output through use of an improved electrode active material.

The present invention relates to a lithium ion battery comprising an electrode including an electrode active material and an electrolytic solution, wherein the electrode active material includes a polyoxometallate which improves the ionic conductivity of the electrode active material and undergoes a redox reaction itself Thereby providing a battery performance improving method.

The present invention also provides an electrode active material additive represented by the following Formula 1:

[Chemical Formula 1]

_{A a} [XM ₁₂ O _40]

(A is at least one ion selected from the group consisting of hydrogen, IA, VIIIA, IB to VIIB elements, rare earth elements, actinides, ammonium, alkylammonium, alkylphosphate and alkylaronium;

X is P5 ⁺ , Si4 ⁺ or ^{B3 +} ;

M is Mo or W)

Also, the present invention provides an electrode mixture of a lithium secondary battery, which comprises 1 to 5% by weight of a compound represented by the following formula (1) based on the total amount of the electrode mixture:

[Chemical Formula 1]

_{A a} [XM ₁₂ O _40]

(A is at least one ion selected from the group consisting of hydrogen, IA, VIIIA, IB to VIIB elements, rare earth element, actinide, ammonium, alkylammonium, alkylphosphate and alkylarononium;

X is P5 ⁺ , Si4 ⁺ or ^{B3 +} ;

M is Mo or W)

The present invention provides a lithium secondary battery comprising the electrode mixture as a positive electrode or a negative electrode.

The electrode active material additive of the present invention improves the ionic conductivity of the electrode active material and performs the redox reaction itself, and the lithium secondary battery including the electrode active material improves the capacity and output of the battery.

The properties of the electrode active material are related to the capacity, cycle characteristics and safety of the battery. The electrode active material may exhibit different capacities depending on charge / discharge rates and other external conditions such as electrolyte selection and electrode formation.

"Capacity" can be defined as the number of Li ions that can be reversibly removed from the crystal structures of lithium-based materials.

"Reversible" means that the structure remains substantially intact and Li can be reinserted into the initial crystal structure.

"Safety" means structural stability or structural integrity and indicates that if the material is decomposed during cycling, gasified or easily decomposed at elevated temperatures, especially if decomposition or gasification occurs within the battery's thermal runaway behavior When inducing initiation, the substance is considered unsafe.

The present invention relates to a lithium ion battery comprising an electrode including an electrode active material and an electrolytic solution, wherein the electrode active material includes a polyoxometallate which improves the ionic conductivity of the electrode active material and undergoes a redox reaction itself Thereby providing a battery performance improving method.

Optically pure polyoxometallates (polyoxometalates, POMs) have diverse potential, including microporous solids, asymmetric catalysts, and inorganic chemicals. The present invention improves ion conductivity by incorporating a polyoxometallate into an electrode active material and contributes to the improvement of the capacity and power of the battery by adding a polyoxometallate which undergoes its own redox reaction within the operating voltage range of the lithium secondary battery .

It is expected that the polyoxometallate having the structure claimed in the present invention is multiplexed within the operating voltage range of a lithium ion battery and performs an electrochemical reaction similar to the self redox reaction and the electrode active material. Accordingly, if the polyoxometallate is included in the electrode active material, the capacity of the battery is expected to be improved.

Specifically, the present invention is characterized by including a polyoxometallate of the following formula (1) in an electrode mixture together with an electrode active material.

[Chemical Formula 1]

_{A a} [XM ₁₂ O _40]

(A is at least one ion selected from the group consisting of hydrogen, IA, VIIIA, IB to VIIB elements, rare earth element, actinide, ammonium, alkylammonium, alkylphosphate and alkylarononium;

X is P5 ⁺ , Si4 ⁺ or ^{B3 +} ;

M is Mo or W)

In the above formula (1), X is preferably P ⁵⁺ , Si ⁴⁺ or B ³⁺ as a hetero element, and M is preferably molybdenum or tungsten as an addenda element.

In particular, the polyoxometallate contained in the electrode mixture of the present invention preferably contains a so-called Keggin anion. The kaggin anion is a hexametallate anion, and typically forms a polyoxometallate such as tungsten phosphate (H ₃ PW ₁₂ O ₄₀ ) or molybdenum phosphate (H ₃ PMo ₁₂ O ₄₀ ).

In order to incorporate the polyoxometallate in the electrode mixture, it is possible to impregnate the electrode active material using a known method such as vacuum impregnating or soaking (U.S. Patent No. 4,633,372), but in the present invention, It can be included in the electrode mixture by a simple method in which the slurry is mixed with the electrode active material in the mixing step. That is, according to the present invention, it is possible to relatively easily provide a means for contributing to the ion conductivity of the electrode active material, the capacity of the battery, and the power output.

On the other hand, when the electrode active material additive of the present invention is included in the negative electrode mixture, the negative active material is dissociated into ions by the water supplied during the mixing process.

The amount of the polyoxometallate contained in the electrode mixture together with the electrode active material of the present invention is preferably 1 to 5% by weight based on the total weight of the electrode mixture.

If the content is less than 1% by weight, the effect is not exhibited. If the content is more than 5% by weight, the relative amount of the electrode active material in the electrode mixture decreases, thereby contributing to improvement of the battery performance.

The present invention provides a method for incorporating a polyoxometallate into a cathode mix. Among the cathode active materials, olivine has a disadvantage in that the output is low due to low ionic conductivity and low electric voltage. Therefore, by forming the electrode mixture together with the polyoxometallate of the present invention, not only the ion conductivity can be improved, but also the battery capacity and the output can be remarkably improved.

The present invention also provides an electrode mixture containing the electrode active material and a lithium secondary battery. The lithium secondary battery of the present invention can be produced by a method known in the art, and is not particularly limited. For example, a separator may be inserted between an anode and a cathode, and a non-aqueous electrolyte may be charged. In addition, the positive electrode, the separator, and the non-aqueous electrolyte, and other additives, if necessary, can be used as is known in the art.

The nonaqueous electrolyte solution of the lithium secondary battery that can be used in the present invention may include a cyclic carbonate and / or a linear carbonate. Examples of the cyclic carbonate include ethylene carbonate (EC), propylene carbonate (PC), and gamma butyrolactone (GBL). Examples of the linear carbonate include at least one selected from the group consisting of diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and methyl propyl carbonate (MPC).

The nonaqueous electrolyte solution of the lithium secondary battery of the present invention comprises a lithium salt together with the carbonate compound. Specific examples of the lithium salt include LiClO ₄ , LiCF ₃ SO ₃ , LiPF ₆ , LiBF ₄ , LiAsF ₆ , and LiN (CF ₃ SO ₂ ) ₂ .

Hereinafter, the present invention will be described in detail with reference to examples.

Example 1

(When the additive is included in the positive electrode mixture)

a. Preparation of a positive electrode containing molybdenum phosphate (H ₃ PMo ₁₂ O ₄₀ )

1 wt% of molybdenum phosphate (H ₃ PMo ₁₂ O ₄₀ ) was mixed with a slurry of a 93 wt% manganese spinel cathode active material, 1 wt% of a conductive material (Acetylene black) and 5 wt% of a PVdF binder, A rear roll press was performed.

b. Cathode manufacturing

92% by weight of carbon powder, 6% by weight of SBR as a binder and 2% by weight of carbon black as a conductive agent were added to water as a negative electrode active material to prepare a negative electrode mixture slurry. The positive electrode mixture slurry was applied to a copper thin film having a thickness of 20 탆 and dried to prepare a negative electrode, followed by roll pressing.

c. Configuration of Unit Battery Cell

A unit cell was formed of the anode and the cathode.

The battery capacity and output characteristics were evaluated for the manufactured battery (using the USABC FreedomCAR test manual).

Example 2

(When the additive is included in the positive electrode mixture)

A unit battery cell was constructed in the same manner as in Example 1, except that tungstophosphate (H ₃ PW ₁₂ O ₄₀ ) was used instead of molybdenum phosphate (H ₃ PMo ₁₂ O ₄₀ ) .

Example 3

(When the additive is included in the negative electrode mixture)

Example manufacture the positive electrode in the first molybdenum phosphate (H ₃ PMo ₁₂ O ₄₀₎ to not do, instead of the negative electrode during manufacture molybdenum phosphate of about 1% by weight of (H ₃ PMo ₁₂ O ₄₀₎ a negative electrode directly into the negative electrode active material slurry comprising . The unit cell was fabricated from the prepared anode and cathode, and then the capacity and output characteristics of the battery were evaluated in the same manner as in Example 1.

Example 4

(When the additive is included in the negative electrode mixture)

A unit battery cell was constructed in the same manner as in Example 3, except that tungstophosphate (H ₃ PW ₁₂ O ₄₀ ) was used instead of molybdenum phosphate (H ₃ PMo ₁₂ O ₄₀ ) in Example 3, .

Example 5

(When the additive is included in both the positive electrode and negative electrode mixture)

The performance of the battery was evaluated in the same manner as in Example 1 by constituting the unit cell according to the anode prepared in Example 1 and the cathode prepared in Example 3.

Comparative Example

A unit cell was constructed in the same manner as in Example 1 except that molybdenum phosphate (H ₃ PMo ₁₂ O ₄₀ ) was not included in the preparation of the anode in Example 1, and the performance of the cell was evaluated.

Relative battery capacity (unit:%) relative to the comparative example Battery output relative to the comparative example (unit:%) Example 1 102% 110% Example 2 105% 112% Example 3 110% 105% Example 4 112% 108% Example 5 108% 113% Comparative Example 100% 100%

As shown in the table, it can be confirmed that the capacity and output characteristics of the battery including the electrode active material additive of the present invention in the positive electrode, negative electrode, or both of the positive electrode and the negative electrode are improved.

Claims (9)

anode; cathode; A lithium secondary battery comprising a separator and a non-aqueous electrolyte, Wherein the positive electrode is formed by coating a positive electrode current collector on a positive electrode current collector, The positive electrode material mixture contains 1 to 5 wt% of a polyoxometallate as a manganese spinel positive electrode active material and a positive electrode active material additive based on the total amount of the positive electrode mixture, Wherein the negative electrode is formed by coating a carbonaceous anode active material on an anode current collector. The lithium secondary battery according to claim 1, wherein the polyoxometallate is represented by the following formula (1). [Chemical Formula 1] _{A a} [XM ₁₂ O _40] (A is at least one ion selected from the group consisting of hydrogen, IA, VIIIA, IB to VIIB elements, rare earth elements, actinides, ammonium, alkylammonium, alkylphosphate and alkylaronium; X is P5 ⁺ , Si4 ⁺ or ^{B3 +} ; M is Mo or W) The lithium secondary battery according to claim 2, wherein the polyoxometallate includes a keggin anion. The lithium secondary battery according to claim 2, wherein the polyoxometallate is tungsten phosphate or molybdenum phosphate. delete delete delete delete delete