KR101868204B1 - Electrode active material, electrode and secondary battery comprising the same - Google Patents

Abstract

Small particles having an average diameter of 3 占 퐉 or less and large particles having an average diameter of 10 占 퐉 or more, wherein the weight ratio of the small particles and the large particles is 1: 1 to 1: 3.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode active material,

The present invention relates to an electrode active material, an electrode including the electrode active material, and a secondary battery, and more particularly, to an electrode active material satisfying high output characteristics and high energy density, an electrode including the same, and a secondary battery.

Recently, interest in energy storage technology is increasing. As the application fields of cell phones, camcorders, notebook PCs and even electric vehicles are expanding, efforts for research and development of electrochemical devices are becoming more and more specified. Electrochemical devices are the most popular field in this respect. Among them, the development of a rechargeable battery capable of charging and discharging has been the focus of attention. In recent years, in developing such a battery, improvement of capacity density and specific energy Research and development on the design of new electrodes and batteries are in progress.

Lithium-containing cobalt oxide (LiCoO ₂ ) is mainly used as a cathode active material of the lithium secondary battery. In addition, a lithium-containing manganese oxide such as LiMnO _{2 having a} layered crystal structure and LiMn ₂ O _{4 having a} spinel crystal structure, (LiNiO ₂ ) is also being considered.

Of the cathode active materials, LiCoO ₂ has excellent properties such as excellent cycle characteristics and is widely used at present. However, LiCoO ₂ has low safety and high cost due to a resource limit of cobalt as a raw material. Lithium manganese oxides such as LiMnO ₂ and LiMn ₂ O ₄ have attracted much attention as a cathode active material that can replace LiCoO ₂ because it has the advantage of using manganese which is abundant in resources and environmentally friendly as a raw material. However, these lithium manganese oxides have disadvantages such as small capacity and poor cycle characteristics.

In addition, the lithium nickel oxide such as LiNiO ₂ has a lower discharge capacity than that of the cobalt oxide when it is charged at 4.25 V, and the reversible capacity of the doped LiNiO _{2 has} a capacity of LiCoO ₂ (about 153 mAh / g) < / RTI > to about 200 mAh / g. Therefore, despite the slightly lower average discharge voltage and volumetric density, commercialized batteries comprising LiNiO ₂ cathode active materials have improved energy density, and therefore, in order to develop a recent high capacity battery, Research is actively under way.

Accordingly, many prior arts focus on improving the characteristics of LiNiO ₂ -based cathode active material and the manufacturing process of LiNiO ₂ , and a lithium transition metal oxide in which a part of nickel is substituted with another transition metal such as Co and Mn is proposed . However, problems such as a high production cost of a LiNiO ₂ -based cathode active material, swelling due to generation of gas in a battery, low chemical stability, and high pH are not sufficiently solved.

Therefore, in some prior arts, there has been an attempt to improve the performance of a battery by applying a material such as LiF, Li ₂ SO ₄ , Li ₃ PO ₄ or the like to the surface of the lithium nickel-manganese-cobalt oxide. In this case, Nickel-manganese-cobalt oxide. Therefore, there is a limitation in exerting a desired level of effect, and a separate process of coating the material on the surface of lithium nickel-manganese-cobalt oxide is required.

However, despite these various attempts, satisfactory lithium complex transition metal oxides have not yet been developed.

Disclosure of Invention Technical Problem [8] The present invention provides a secondary battery including an electrode active material mixed with a large particle and a small particle, and having improved output characteristics and energy density at the same time.

Also, there is provided a secondary battery in which the large particles and the small particles are mixed at an optimum ratio and little influence is exerted by the porosity.

Other objects and advantages of the present invention will become apparent from the following description. It is also to be easily understood that the objects and advantages of the present invention can be realized by the means or method described in the claims, and the combination thereof.

According to an aspect of the present invention, there is provided a method for manufacturing a semiconductor device, the method comprising the steps of: preparing a semiconductor substrate having a plurality of small particles having an average diameter of 3 탆 or less and a large particle having an average diameter of 10 탆 or more, Is provided.

The electrode active material may be a cathode active material.

At least one of the small particles and the large particles may be a nickel-manganese-cobalt ternary material.

The nickel-manganese-cobalt ternary material may be a lithium-nickel-manganese-cobalt composite oxide (NMC) represented by the following formula.

≪

_{Li (1 + δ) Mn x} Ni y Co (1-xyz) M z O 2 (M is Ti, Zr, Nb, Mo, W, Al, Si, Ga, at least one selected from the group consisting of Ge and Sn 0.15 <? 0.15, 0.1 <x? 0.5, 0.6 <x + y + z <1.0, 0? Z? 0.1).

According to another aspect of the present invention, there is provided an electrode including an electrode current collector and an electrode layer formed on at least one surface of the electrode current collector and including the above-described electrode active material.

The rolling density of the electrode layer may be 3.0 g / cc or more.

The electrode layer may have a porosity of 20 to 40%.

The electrode may be a cathode.

According to another aspect of the present invention, there is provided an electrochemical device including the electrode.

The electrochemical device may be a lithium secondary battery.

The lithium secondary battery may have a resistance of 1 to 5 [Omega].

The present invention is advantageous in that the low-temperature and normal-temperature output characteristics are excellent and the degradation due to repetition of high-temperature storage and cycling is improved by using a small particle having an optimum average diameter and a large particle, respectively.

In addition, mixing small particles and large particles at an optimum weight ratio has an advantage of having excellent rolling density and high packing density, and a problem that can be caused by rolling at low porosity without showing the influence of porosity There is an advantage that the problem of low contact between particles at high porosity can be solved.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate preferred embodiments of the invention and, together with the description of the invention, It is not interpreted.
Fig. 1 is a graph showing the particle distribution of the electrode active material used in Comparative Example 5 and Comparative Example 6. Fig.
2 is a graph showing the rolling density according to the small particle content of the cathode prepared in Examples 1 and 2 and Comparative Examples 1 to 4.
3 is a graph showing the results of the high temperature cycle of Example 4, Comparative Example 5, and Comparative Example 6;
4 is a graph showing low-temperature output characteristics of Example 4, Comparative Example 5 and Comparative Example 6. Fig.
5A and 5B are SEM photographs of an electrode having a 25% porosity as a cathode active material used in Comparative Example 5 and Comparative Example 6, respectively.

Hereinafter, the present invention will be described in detail. The terms or words used in the present specification and claims should not be construed in a conventional or dictionary sense and the inventor shall appropriately define the concept of the term in order to explain its invention in the best way The present invention should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention, and not all of the technical ideas of the present invention are described. Therefore, at the time of the present application, It should be understood that various equivalents and modifications are possible.

The electrode active material according to an embodiment of the present invention includes two kinds of electrode active materials having different diameters, preferably small particles having an average diameter of 3 μm or less and a large particle having an average diameter of 10 μm or more, The weight ratio of the small particle and the large particle is 1: 1 to 1: 3, preferably 1: 2 to 1: 3, more preferably 1: 2.5 to 1: 3.

In the case of manufacturing an electrode using an electrode active material composed only of small particles in the past, the low-temperature / normal-temperature output characteristics are excellent, but there is a serious problem of degradation due to high-temperature storage and cycle. Conversely, The electrode has a low temperature / room temperature output characteristic but has a small degradation due to high temperature storage and cycle.

In order to complement the above problems, the electrode active material of the present invention is mixed with large particles and small particles. In order to overcome the above problems and simultaneously exhibit the advantages of each particle, the small particles have an average diameter of 3 μm or less Preferably 1 to 3 mu m, more preferably 2 to 3 mu m, and the mean diameter of the substituent is 10 mu m or more, preferably 10 to 30 mu m, more preferably 10 to 20 mu m.

In the case of large particles, the influence of porosity is not great. However, when electrodes are manufactured using only small particles, there is a problem that resistance increases at high or low porosity. In order to solve the above problem, The present invention has the effect of solving the problem of the conventional small particle having the influence of porosity by mixing the large particles at a weight ratio of 1: 1 to 1: 3, and at the same time, Can be solved, and there is an effect of solving low contact between particles at high porosity.

At this time, the electrode active material may be a cathode active material, and the cathode active material applicable to the present invention may be any material capable of intercalating-deintercalating ions during charging and discharging, Li _{(1 + delta)} Mn _x Ni _y Co _(1-xyz) M _z O ₂ where M is Ti, Zr _(1-xyz) , or the like, and is preferably a lithium / nickel / manganese / cobalt composite oxide 0.15 < = 0.15, 0.1 < x < = 0.5, 0.6 < x + y + z < = 0.15 and at least one element selected from the group consisting of Nb, Mo, W, Al, Si, Ga, 1.0, 0? Z? 0.1)).

The electrode according to another embodiment of the present invention may include an electrode current collector and an electrode layer formed on the electrode current collector and including any one of the electrode active materials described above.

The electrode current collector is not particularly limited as long as it has high conductivity without causing any chemical change in the related art. Examples of the electrode current collector include stainless steel, aluminum, nickel, titanium, sintered carbon or aluminum or stainless steel Surface-treated with carbon, nickel, titanium, silver, or the like may be used.

The electrode current collector may have fine irregularities on its surface to increase the adhesive force of the electrode active material. Various types of electrode layers such as a film, a sheet, a foil, a net, a porous body, a foam, cc or more, preferably 3.0 to 4.5 g / cc. When the rolling density is less than 3.0 g / cc, the thickness of the electrode may increase to increase the cell thickness, There is a problem that nonuniformity of the distribution can be increased.

The porosity of the electrode layer may be in the range of 20 to 40%, preferably 25 to 35%. If the porosity is less than 20%, the surface of the electrode may be clogged to cause electrolyte impregnation, , There is a problem that the contact between the active material and the conductive material is insufficient and the electronic conductivity is greatly reduced.

The electrode may be an anode or a cathode, preferably a cathode.

According to another embodiment of the present invention, there is provided an electrochemical device including the above-described electrode, wherein the electrochemical device may be a lithium secondary battery.

At this time, the lithium secondary battery may have an electrical resistance of 1 to 5?, Preferably 1.5 to 3?, Particularly when the resistance exceeds 5 ?, the cycle of the cell and the deterioration of the cell during storage are accelerated there is a problem.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art.

Manufacture of cathode

[Example 1]

The average diameter of 2㎛ of _{LiMn 1/3 Ni 1/3 Co 1/3 O 2} : 92 A cathode active material mixed in a weight ratio of 3: 20㎛ of LiMn _1/3 Ni _1/3 Co _1/3 O ₂ 1 a By weight, 4% by weight of carbon black as a conductive material, and 4% by weight of PVDF as a binder were added to N-methyl-2-pyrrolidone (NMP) as a solvent to prepare a cathode mixture slurry. The cathode mixture slurry was applied to an aluminum (Al) thin film of a cathode current collector having a thickness of 20 탆 and dried to form a cathode, followed by roll pressing.

[Example 2]

The cathode active material mixed in a weight ratio of 1: average diameter of 2㎛ of _{LiMn 1/3 Ni 1/3 Co 1/3 O 2} : 20㎛ of LiMn _1/3 Ni _1/3 Co _1/3 O ₂ to 1 The cathode was prepared in the same manner as in Example 4, except that the cathode was used.

[Comparative Example 1]

92% by weight of LiMn _1/3 Ni _1/3 Co _1/3 O ₂ having an average diameter of 2 μm as a cathode active material, 4% by weight of carbon black as a conductive material, and 4% by weight of PVDF as a binder Methyl-2-pyrrolidone (NMP) to prepare a cathode mixture slurry. The cathode mixture slurry was applied to an aluminum (Al) thin film of a cathode current collector having a thickness of 20 탆 and dried to form a cathode, followed by roll pressing.

[Comparative Example 2]

A cathode was prepared in the same manner as in Comparative Example 1, except that LiMn _1/3 Ni _1/3 Co _1/3 O ₂ having an average diameter of 20 μm was used as a cathode active material.

[Comparative Example 3]

LiMn _1/3 Ni _1/3 Co _1/3 O _{2 having an} average diameter of ₂ μm: LiMn _1/3 Ni _1/3 Co _1/3 O ₂ having an average diameter of 20 μm was mixed at a weight ratio of 3: 1 A cathode was prepared in the same manner as in Comparative Example 1, except that the cathode active material was used.

[Comparative Example 4]

LiMn _1/3 Ni _1/3 Co _1/3 O _{2 having an} average diameter of ₂ μm: LiMn _1/3 Ni _1/3 Co _1/3 O ₂ having an average diameter of 20 μm was mixed at a weight ratio of 5:95 A cathode was prepared in the same manner as in Comparative Example 1, except that the cathode active material was used.

Manufacture of anode

(N-vinylpyrrolidone) as the anode active material, lithium vinylidene fluoride (PVdF) as the binder, and carbon black as the conductive material in the amounts of 96 wt%, 3 wt% and 1 wt%, respectively, Methyl-2-pyrrolidone (NMP) to prepare an anode mixture slurry. The anode mixture slurry was applied to a copper (Cu) thin film as an anode current collector having a thickness of 10 占 퐉 and dried to produce an anode, followed by a roll press.

Preparation of Membrane

On the surface of the high-density polyethylene porous polymer film substrate, BaTiO ₃ and Polyvinylidene fluoride, and polyvinylidene fluoride-hexafluoropropylene were coated to prepare a separator.

Manufacture of lithium secondary battery

[Example 3]

The cathode, the anode and the separator prepared in Example 1 were assembled using a stacking method, and ethylene oxide (LiPF ₆ ) dissolved in 1 M of lithium hexafluorophosphate (LiPF ₆ ) was added to the assembled battery. EC / EMC = 1: 2, volume ratio) system electrolyte was injected to prepare a lithium secondary battery.

[Example 4]

A lithium secondary battery was produced in the same manner as in Example 3, except that the cathode prepared in Example 2 was used.

[Comparative Example 5]

The cathode, the anode and the separator fabricated in Comparative Example 1 were assembled using a stacking method. Ethylene carbonate (LiPF ₆ ) dissolved in 1 M of lithium hexafluorophosphate (ethylmethyl carbonate EC / EMC = 1: 2, volume ratio) system electrolyte was injected to prepare a lithium secondary battery.

[Comparative Example 6]

A lithium secondary battery was produced in the same manner as in Comparative Example 5 except that the cathode prepared in Comparative Example 2 was used.

[Comparative Example 7]

A lithium secondary battery was produced in the same manner as in Comparative Example 5, except that the cathode prepared in Comparative Example 3 was used.

[Comparative Example 8]

A lithium secondary battery was produced in the same manner as in Comparative Example 5 except that the cathode prepared in Comparative Example 4 was used.

Performance evaluation

[Rolling density measurement]

5 g of the cathode prepared in Examples 1 and 2 and Comparative Examples 1 to 4 was placed in a circular holder having a diameter of 10.0 mm and the density was measured while increasing the pressure from 13 MPa to 64 MPa by 13 MPa. , And that the battery according to the present invention had an excellent rolling density and packing density as compared with the battery of the comparative example.

[High temperature cycle measurement]

The lithium secondary batteries prepared in Example 3 and Comparative Examples 5 and 6 were subjected to a 1 C / 2 C cycle at 45 ° C and a room temperature (25 ° C) capacity and resistance were measured every 100 cycles. The resistance of the battery of Example 3 according to the present invention is shown in FIG. 3 by measuring resistance by calculating the voltage difference after flowing the 5C pulse for 10 seconds while maintaining the state of charge 50%. In the case of the battery of Example 3 according to the present invention, It can be confirmed that the high-temperature storage characteristics of Comparative Example 5 composed of only small particles are maintained. This shows that the conventional problem of solely using the substitute as in Comparative Example 6 is solved.

[-30 ℃ Output Measurement]

The lithium secondary batteries prepared in Example 3, Comparative Example 5, and Comparative Example 6 were stored at -30 캜 for 2 hours, and a 1 C constant current was applied to measure the discharge output. The discharge output can be calculated using the following equation after the constant current is applied for 40 seconds after the voltage difference.

[Influence measurement of porosity]

Lithium rechargeable batteries including electrodes having porosity of 25%, 30%, 33%, 36%, and 40% were manufactured using the cathode active material used in Example 3, Comparative Example 5 and Comparative Example 6, 4, and the comparative example 5 composed of small particles was largely affected by the porosity. On the other hand, in the case of Comparative Example 5 composed of small particles, Example 3 was not largely affected by porosity, and was measured to be nearly similar to 2 for a comparison consisting only of an acceptor.

5A is an SEM photograph of an electrode having a 25% porosity as a cathode active material used in Comparative Example 5, and FIG. 5B is an SEM photograph of an electrode having a 25% porosity as a cathode active material used in Comparative Example 6. 5A and 5B, there is a problem that the small particle electrode including only small particles and having a porosity of 25% is excessively pressed on the upper portion of the electrode to clog the upper portion of the electrode, and when the porosity is 40% And the cell performance is reduced. In addition, when only the substituent is included, the output characteristics are not greatly affected, but a large number of the upper portions of the electrode may be broken at a porosity of 25% when the electrode cross section is checked. However, when large particles and small particles are mixed, it is confirmed that all of these phenomena are alleviated and the influence on porosity is reduced.

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 as defined in the appended claims.

Claims (11)

delete delete delete delete Electrode collector; And
And an electrode layer formed on at least one surface of the electrode current collector,
The electrode layer is composed of a lithium-nickel-manganese-cobalt composite oxide (NMC) having a mean diameter of 1 to 3 μm and a lithium-nickel-manganese-cobalt composite oxide (NMC) having a mean diameter of 10 to 30 μm 1: 1 to 1: 3,
The electrode layer has a rolling density of 3.0 g / cc or more and a porosity of 20 to 40%
The lithium-nickel-manganese-cobalt composite oxide (NMC) is represented by the following formula:
&Lt;
Li _{(1 +?)} Mn _x Ni _y Co _(1-xyz) M _z O ₂
Wherein M is at least one element selected from the group consisting of Ti, Zr, Nb, Mo, W, Al, Si, Ga, Ge and Sn and satisfies -0.15 &lt; , 0.6 < x + y + z < 1.0, 0? Z? 0.1). delete delete 6. The method of claim 5,
Wherein the electrode is a cathode. An electrochemical device comprising the electrode of claim 5. 10. The method of claim 9,
Wherein the electrochemical device is a lithium secondary battery. 11. The method of claim 10,
Wherein the lithium secondary battery has a resistance of 1 to 5 [Omega].

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