KR20090074428A - Igh voltage, high coulomb efficiency and good cycliability lithium ion secondary battery - Google Patents

Abstract

A lithium ion secondary battery is provided to ensure high efficiency and high-capacity by using a negative electrode having coulomb efficiency, high specific capacity and excellent cycle lifetime property. A lithium ion secondary battery comprises a negative electrode with initial coulombic efficiency of 90% or greater, a positive electrode with an LiCoO2 positive electrode active material, and an ion conductor. The negative electrode comprises a negative electrode active material including a non-carbonaceous, a binder, and a conductive material.

Description

High Voltage High Efficiency Long Life Lithium Secondary Battery {igh Voltage, High Coulomb Efficiency And Good Cycliability Lithium Ion Secondary Battery}

The present invention relates to a lithium secondary battery, and more particularly, to a lithium secondary battery having a positive electrode manufactured using a LiCoO ₂ positive electrode material and a high capacity non-carbon-based negative electrode, which can be charged even in a high voltage environment of 4.2 to 4.5V. That is, a method of manufacturing a high capacity cathode using a silicon compound, alloy material, etc. based on a non-carbon-based anode active material, and a high capacity high efficiency cathode electrode exhibiting a high initial coulombic efficiency through pretreatment of the electrode and the high capacity It relates to a high capacity high energy lithium secondary battery comprising a high efficiency negative electrode.

 Recently, the development of the electronic and information communication industry is showing rapid growth through the portable, miniaturized, lightweight, and high-performance electronic devices. Therefore, high-performance lithium secondary batteries are employed as power sources for these portable electronic devices, and demand is increasing rapidly. Secondary batteries used with repeated charging and discharging are essential as power sources for portable electronic devices, electric bicycles, and electric vehicles for information and communication. In particular, since their product performance depends on batteries, which are core components, the demand for high performance batteries is very large. The characteristics required for the battery include various aspects such as charge and discharge characteristics, lifespan, high rate characteristics, and stability at high temperatures, and lithium secondary batteries are most commonly used.

Since lithium secondary battery was commercialized at high capacity level of 900 mAh based on 18650 battery in 1992, technology has been developed up to 2600 mAh level based on 18650 battery in 2007. Due to such high-performance battery characteristics, demand for medium and large-sized batteries such as electric vehicles and batteries with high output characteristics is steadily increasing.

The lithium secondary battery is mainly composed of a positive electrode, a negative electrode, an electrolyte, a separator, a packaging material, and the like. The positive electrode is formed by binding a mixture of a positive electrode active material, a conductive agent, and a binder to a current collector. Lithium transition metal compounds such as LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , and LiMnO ₂ are mainly used as the positive electrode active material. Surface-modified cathode active materials are also used. These materials are charged / discharged as lithium ions intercalate / deintercalation into the crystal structure and have a high electrochemical reaction potential. Lithium metal, carbon or graphite is mainly used as the negative electrode active material and has a low electrochemical reaction potential as opposed to the positive electrode active material. Lithium metal is inadequate as a secondary battery material because of poor cycle characteristics, and carbon-based materials are currently being used in commercial batteries, and new materials are being developed that surpass the characteristics of carbon-based materials in terms of capacity, initial coulombic efficiency, and cycle life. Electrolyte solution is mainly composed of LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ , LiPF ₆ , LiBF ₄ , LiClO ₄ , LiN ( A salt containing lithium ions such as SO ₂ C ₂ F ₅ ) ₂ and LiBOB is dissolved and used.

In recent years, the battery system has been undergoing a high voltage due to the high capacity of the battery. In the case of the conventional lithium secondary battery was charged at a charge voltage of 3.0V to 4.2V, but the research to seek a higher energy capacity by applying a higher charge voltage (4.2 ~ 4.5V).

However, in the case of using a negative electrode, a positive electrode, and a non-aqueous carbonate-based solvent which is commonly used as an electrolyte, when the battery is charged at a voltage higher than the normal charge potential of 4.2 V, the oxidizing power is increased. As the decomposition reaction of the electrolyte proceeds, there is a problem in that the life characteristics rapidly drop.

On the other hand, the amount of the cathode material is dramatically increased. Graphite materials have a theoretical specific capacity of 372 mAh / g and a density of 2.62 g / ml, but for silicon-based materials under development, the theoretical cost is 4200 mAh / g, and the density is 2.33 g / ml. The transition potential also has similar characteristics to graphite.

Most of the high-capacity non-carbon electrode materials such as silicon or tin have low initial coulombic efficiency, and the specific cost of lithium desorption process increases as the cycle progresses. Silicon oxide (SiO) is Li during initial charging (reduction) process. This insertion causes Li ₂ O to generate irreversible specific cost, and the initial charge-discharge coulomb efficiency is lowered from 40% to 80%, so that graphite having an initial charge-discharge coulomb efficiency of 90% or more is not suitable for practical application. it's difficult.

The present invention is to solve the above problems,

It provides a high energy next-generation lithium secondary battery negative electrode using a non-carbon-based material based negative active material exhibits a low initial coulombic efficiency but high specific capacity.

In addition, the initial coulombic efficiency and high capacity characteristics are improved by improving the initial coulombic efficiency through a pretreatment process of a high energy next-generation lithium secondary battery negative electrode using a non-carbon-based material-based negative electrode active material having low initial coulombic efficiency. It provides an electrode manufacturing method that can be applied to the negative electrode, which can be expressed together with the positive electrode,

In addition, by using the negative electrode for the next-generation lithium secondary battery exhibiting the high initial coulombic efficiency and high specific capacity characteristics, the next-generation lithium secondary battery surpasses the carbon-based lithium secondary battery by dramatically improving the energy storage capacity of the existing lithium secondary battery. It aims to provide.

The present invention for achieving the above object

A negative electrode including a negative electrode active material, a binder, and a conductive material including a non-carbon compound including at least one of silicon oxide and tin oxide, and having an initial coulombic efficiency of 90% or more; LiCoO ₂ A positive electrode including a positive electrode active material; And it provides a lithium secondary battery having an ion conductor.

In addition, the negative electrode provides a lithium secondary battery, characterized in that obtained by performing a reduction pretreatment process.

In addition, the reduction pretreatment process provides a lithium secondary battery, characterized in that after the reduction to a constant voltage of 0V within a range of 1 to 60 hours, and then to 0V through a constant current.

In addition, the non-carbon-based compound provides a lithium secondary battery characterized in that the alloy with graphite (graphite).

In addition, the mixing weight ratio of the non-carbon compound and graphite provides a lithium secondary battery, characterized in that in the range of 4: 6 ~ 6: 4.

In addition, the silicon oxide provides a lithium secondary battery, characterized in that the range of x in SiOx is in the range of 0.5 ~ 1.5.

In addition, the silicon oxide provides a lithium secondary battery, characterized in that the range of x in SiOx is in the range of 0.5 ~ 1.5.

In addition, it provides a lithium secondary battery, characterized in that the charge at a charging voltage within the range of 4.2V to 4.5V.

Hereinafter, the present invention will be described in detail.

Lithium secondary battery according to the present invention comprises a negative electrode active material, a binder and a conductive material comprising a non-carbon-based compound containing at least one of silicon oxide and tin oxide; LiCoO ₂ And a positive electrode including a positive electrode active material and an ion conductor.

1 shows a lithium secondary battery 1 which is an embodiment of the present invention. The lithium secondary battery 1 includes a negative electrode 2, an electrode 3, a separator 4 disposed between the negative electrode 2 and the positive electrode 3, the negative electrode 2, the positive electrode 3, and the separator 4. ), The ion conductor impregnated in the ()), the battery container (5), and the sealing member (6) for sealing the battery container (5) as a main portion. The shape of the lithium secondary battery illustrated in FIG. 1 may be in a cylindrical shape, but also in various shapes such as a cylindrical shape, a square shape, a coin shape or a sheet shape.

First, the negative electrode for a lithium secondary battery according to the present invention will be described.

The negative electrode for a lithium secondary battery according to the present invention is a negative electrode for a lithium secondary battery including a negative electrode active material, a binder, and a conductive material containing a non-carbon compound, and has an initial coulombic efficiency of 90% or more.

The non-carbon electrode material has not been applied to a commercial lithium secondary battery due to problems of initial coulombic efficiency and cycle characteristics despite a high specific capacity, but the present invention solves this problem.

The negative active material includes the non-carbon compound, but is not limited thereto and includes at least one of a silicon oxide compound and a tin oxide compound. The silicon oxide has a range of SiO _x to x in the range of 0.1 to 2, preferably in the range of 0.5 to 1.5, and more preferably in the range of 0.9 to 1.1, the characteristics of the active material are excellent.

In particular, the non-carbon-based compound is preferably alloyed with graphite to have the form of a composite. In this case, the weight ratio of non-carbon compound such as silicon oxide and graphite is not limited, but is preferably in the range of 2: 8 to 7: 3 as the weight ratio, and particularly preferably the weight ratio is in the range of 4: 6 to 6: 4. Do. According to the experimental results, it was excellent at the composition ratio of about 5: 5. This is because graphite may serve as a matrix to alleviate the volume expansion of the non-carbon compound.

Although not limited by the alloying method, as an example, a composite is prepared by ball milling a mixture of a non-carbon compound and graphite together with stainless balls at a predetermined revolutions per minute in an inert atmosphere such as argon or nitrogen using a ball milling machine, and silicon oxide The method of heat-processing the composite material of and graphite in inert atmosphere, such as argon and nitrogen, is mentioned.

The present invention does not specify the material of the ball with respect to the stainless ball, and can be used as long as it is a ball of a material showing the function of mechanical ball milling. Bowling machine in the present invention is used as a means for imparting the kinetic energy to the ball is not limited to a specific bowling machine. Maintaining an inert atmosphere during ball milling and heat treatment in the present invention is for the purpose of preventing oxidation of the material and can be used according to the oxidation characteristics of the material.

Furthermore, when the carbon material is applied to the non-carbon-based compound alloyed with the graphite, it is possible to reduce the volume expansion of the alloy material while smoothing the electronic conductivity, it can be developed as a high capacity long life electrode material by optimizing the carbon material coating content have.

The coating method of the carbon material is not limited, but a chemical vapor deposition (CVD) method using volatile carbon precursor vapor may also be used, and any method capable of adding and compounding the carbon material is within the scope of the present invention.

In particular, the carbon precursor can be obtained by carbonizing the carbon precursor through a heat treatment in an inert atmosphere such as argon or nitrogen by sufficiently stirring the carbon precursor material in the composite of silicon oxide and graphite under the same conditions as in the production of the primary composite of silicon oxide and graphite. .

The carbon precursor is not limited as long as it is a material that can provide carbon so that carbon can be applied to the composite by carbonization, and it is preferable to use pitch, polymer, or organic compound materials. In particular, vinyl resins such as polyvinylidene fluoride (PVDF) and polyvinyl chloride (PVC), conductive polymers such as polyaniline (PAn), polyacetylene, polypyrrole, polythiophene, and the like The conductive polymer may be a conductive polymer doped with hydrochloric acid or the like. Carbon precursors are particularly preferred polyvinylchloride (PVC).

The heat treatment temperature may be used in the range of 500 ° C to 3000 ° C, preferably in the range of 700 ° C to 1200 ° C, and more preferably in the range of 800 ° C to 1000 ° C.

After the heat treatment step, may further comprise the step of grinding and classifying the obtained material.

The binder is not limited, but various adhesive properties such as fluorinated polymer materials such as polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMS, carbonxymethylcellulose), and styrene-butadiene rubber (SBR) It is advisable to use at least one material with

A conductive material may be added and used for the purpose of improving the electron conductivity of the negative electrode active material, and mainly a fine powder carbon-based material may be used and a material of metallic or conductive polymer may be used. As the carbon-based fine powder, at least one of various materials such as carbon black, carbon nanotube, carbon nanofiber and graphite fine powder can be used. Both composite walls can be used.

A solvent may be used for slurrying, and a high dielectric constant organic solvent such as NMP (N-methyl pyrrolidone) or DMF (dimethyl formamide) may be used, and water (H 2 O) may also be used as a solvent. It can be used and there is no limitation on the solvent.

The negative electrode active material is prepared as a slurry together with a binder, a conductive material, and the like to prepare an electrode. Among the negative electrode active materials, conductive materials and bonding materials forming the electrode solids, the weight percent of the negative electrode active materials can be used in the range of 99% to 50% by weight, and the weight percentage of the conductive material can be used in the range of 0% to 30% by weight. And the weight percent of the bonding material can be used in the range of 1 weight percent to 40 weight percent.

In particular, the negative electrode for a lithium secondary battery according to the present invention is manufactured by performing a reduction pretreatment process to be described later, that is, a characteristic that cannot be seen in a non-carbon-based active material, that is, an initial coulombic efficiency of 85% or more, particularly 90% or more (97% in the described embodiment) It came out very excellently above)). A more detailed description will be described later in the manufacturing method.

Hereinafter, a method of manufacturing a negative electrode according to the present invention will be described. Description is abbreviate | omitted about the matter described in description of said negative electrode for lithium secondary batteries.

The negative electrode manufacturing method according to the present invention is not limited, but preparing an electrode slurry by mixing a component including an active material, a binder, and a conductive material including a non-carbon compound, applying the electrode slurry to a current collector and drying the electrode to form an electrode. Step, it may be made, including the step of pre-reduction of the formed electrode. Herein, the active material, the binder, and the conductive material are not particularly limited, and the active material, the binder, and the conductive material may be used.

First, an electrode slurry is prepared.

Among the negative electrode active materials, conductive materials and bonding materials forming the electrode solids, the weight percent of the negative electrode active materials can be used in the range of 99% to 60% by weight, and the weight percentage of the conductive material can be used in the range of 0% to 30% by weight. And the weight percent of the bonding material can be used in the range of 1 weight percent to 40 weight percent. A mixture of the above conditions is mixed using a mixer to prepare an electrode slurry.

Next, the prepared electrode sludge is applied onto a thin copper current collector and dried to prepare an electrode plate. The method for producing the electrode plate from the electrode slurry may use a method commonly used in the art and is not limited.

Next, the formed negative electrode is subjected to reduction pretreatment, followed by oxidation pretreatment as necessary.

2 is a diagram showing an example of a reduction pretreatment and an oxidation pretreatment method. The prepared electrode plate is treated according to one process diagram as shown in FIG. 2 to produce a negative electrode plate having high coulombic efficiency, high specific capacity and long lifetime.

In the process of FIG. 2, the reduction pretreatment process shown in FIG. 2 comprises a lithium counter electrode for reduction pretreatment of ② and a lithium reference electrode for reduction pretreatment of ④ in an electrolytic cell containing an organic electrolyte solution for reduction pretreatment of ③ and according to a continuous process. The electrode plate of ① is supplied to a reduction pretreatment electrolyzer. The lithium reference electrode for reduction pretreatment (4) is used for the purpose of more accurately measuring the potential of the electrode plate, and in some cases, the electrode of the electrode may be used as the potential of the electrode plate. In this case, ② serves as a function of the counter electrode and the reference electrode. Charging of the electrode plate during the reduction pretreatment may be performed on the basis of voltage or electric quantity. The residence time in the electrolyzer is important as a major factor affecting the diffusion of lithium ions into the negative electrode active material. As a method of adding or subtracting the electrolytic cell retention time, a method of adjusting the speed of the electrode plate progression, a method of adjusting the length of the electrolytic cell, a method of installing an additional roller inside the electrolytic cell, and the like can be used. You can add or subtract the plate immersion time.

In the process of FIG. 2, the pre-reduction step can be easily performed by shorting the electrode plate of ① and the lithium counter electrode for reduction pretreatment of ② to be charged at a constant voltage of 0 V without controlling the voltage or electric quantity of the reduction pretreatment process of the partial process. .

In the process of FIG. 2, the oxidation pretreatment process of the Z partial process is similar to the reduction pretreatment process of the Z partial process, and is an electrolytic cell process for the pretreatment of the oxidation (discharge) process to increase the potential of the electrode. Various electrochemical conditions such as the potential of the oxidation process and the retention time can be adjusted for the purpose of the electrode manufacturer.

In the process of Figure 2, the partial process is configured for the purpose of washing the electrolyte salt contained in the electrode, and may be composed of an organic solvent constituting the electrolyte or one or more of these organic solvents, within a range that does not damage the electrode Any solvent can be used.

In the process of FIG. 2, the chopped partial process may transition to the chopped partial process without cleaning, depending on the purpose of the electrode manufacturer.

In the process of Figure 2, the partial process is for drying the electrode, the drying temperature and the retention time is configured according to the purpose of the electrode manufacturer.

In the process of FIG. 2, the oxidation pretreatment process shown in FIG. 2 is a part necessary for manufacturing the electrode in a continuous process separately from the reduction pretreatment process. The oxidation pretreatment of ㉡ consists of a lithium counter electrode for oxidation pretreatment ⑤ and a lithium reference electrode for oxidation pretreatment ⑥ in an electrolytic cell containing an organic electrolytic solution for reduction pretreatment of an electrolytic cell ③. It is supplied from the pretreatment electrolyzer to the oxidation pretreatment tank. The lithium reference electrode for oxidation pretreatment of ⑥ is used for the purpose of more accurately measuring the potential of the electrode plate, and in some cases, the electrode of the electrode ⑤ may be used. In this case ⑤ also serves as the counter electrode and reference electrode of the oxidation pretreatment. The discharge of the electrode plate during the oxidation pretreatment is performed on a voltage basis. As a method of adding or subtracting the retention time for the electrolyzer, a method of adjusting the speed of the electrode plate progression, a method of adjusting the length of the electrolyzer, and a method of installing an additional roller inside the electrolyzer may be used. By this, the immersion time of the electrode plate can be reduced.

세정 cleaning tank is for cleaning the electrolyte solution impregnated with the electrode. It uses an organic solvent, consists of a low boiling point organic solvent constituting the organic electrolyte solution, and can be used as a cleaning solution by selecting a solvent in a range that does not dissolve the binder. .

The drying tank of ㉣ is a process of drying the organic solvent impregnated to the electrode.

In the case of producing an electrode in a battery factory and continuously introducing it into a battery manufacturing process, the washing tank process of the tank and the drying tank process of the tank can be omitted.

In addition, when the pretreated electrode plate is stored in a dry space that faithfully manages moisture and is used for battery manufacturing, the cleaning process can be omitted.

FIG. 3 is an example method of eliminating oxidation pretreatment in the process of FIG. 2. The process used in the process of Figure 2 is a process of solving the irreversible specific amount through the electrochemical reduction process and oxidation process. In Figure 3 is a method of reducing the electrode plate by charging the amount of electricity corresponding to the irreversible specific amount. The result of the present method leads to the same result as the result of FIG. In order to produce an electrode plate in a continuous process, after charging the amount of electricity corresponding to the irreversible specific amount, the potential of the electrode plate reaching the potential equilibrium is obtained, and constant voltage charging is performed on the pole plate of continuous transfer to this potential.

This electrode pretreatment process can increase the initial coulombic efficiency of not only the silicon oxide anode, but also all kinds of cathodes, and can express the specific amount at a high value from the beginning. In addition, the pretreatment process of the present invention is not limited to the negative electrode, and can be easily applied to the improvement of one process even for the positive electrode having low initial coulombic efficiency or poor initial specific capacity expression characteristics. Therefore, the electrode manufacturing method can be applied to the manufacturing method of the positive electrode as well as the negative electrode.

Next, the anode will be described. As a positive electrode active material, as a result of various experiments, LiCoO ₂ was found to be organically well-combined with the above-described negative electrode in a high voltage charging environment, and the battery life was excellent, and thus LiCoO ₂ was selected as the positive electrode active material.

The positive electrode is preferably made of a positive electrode mixture consisting of a positive electrode active material, a conductive material and a binder, the conductive material and the binder may be those listed in the description of the negative electrode material, and the content is described above in detail, so the description is omitted.

The anode may also go through a reduction pretreatment process as described above.

Next, the ion conductor is propylene carbonate (hereinafter referred to as PC), ethylene carbonate (hereinafter referred to as EC), butylene carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyl tetrahydrofuran and γ-butyrolactone as electrolytes. , Dioxolane, 4-methyldioxolane, N, N-dimethylformamide, dimethylacetoamide, dimethylsulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, dimethyl Carbonate (hereinafter referred to as DMC), ethylmethyl carbonate (hereinafter referred to as EMC), diethyl carbonate, methylpropyl carbonate, methylisopropyl carbonate, ethylbutyl carbonate, dipropyl carbonate, diisopropyl carbonate, dibutyl carbonate, diethylene glycol, LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ , LiPF ₆ , LiBF ₄ , Li in an aprotic solvent such as dimethyl ether or a mixed solvent in which two or more of these solvents are mixed One or a mixture of two or more electrolytes composed of lithium salts such as ClO ₄ , LiBOB, and LiN (SO ₂ C ₂ F ₅ ) ₂ may be used.

In addition, a polymer solid electrolyte may be used instead of the electrolyte solution. In this case, it is preferable to use a polymer having high ion conductivity with respect to lithium ions, and polyethylene oxide, polypropylene oxide, polyethyleneimine and the like can be used. The solvent and the solute may be added to the polymer of to form a gel.

As the separator, an olefin porous film such as polyethylene or polypropylene may be used, and other known techniques may be applied or subtracted and included in the present invention.

A non-carbon-based new anode with high coulombic efficiency, high specific capacity, and excellent cycle life characteristics, which is manufactured by using an active material using non-carbon compounds such as silicon oxide and tin oxide and graphite materials The electrochemical characterization of the lithium secondary battery with the positive electrode manufactured by using the LiCoO2 cathode material and the invention as a lithium secondary battery with high efficiency and high capacity even in a high voltage environment of 4.2 ~ 4.5V invented.

Hereinafter, the present invention will be described in detail through examples. However, the following examples are only preferred embodiments of the present invention and are not intended to limit the scope of rights defined by the claims.

<Example 1>

A negative electrode active material composite was prepared by ball milling a mixture of silicon monoxide and graphite in a 5: 5 weight ratio with a stainless steel ball (2 grams / ball) for 24 hours at 350 revolutions per minute in an inert atmosphere of argon using a ball mill. .

Subsequently, 50% by weight of the negative active material, 15% by weight of PVDF-HFP binder, 32% by weight of dibuthyl phthalate plasticizer, and 3% by weight of SPB (super P black) conductive material were used as ethylenepyrrolidone as a solvent. An electrode slurry was prepared. After applying the prepared electrode slurry to PET and dried, a negative electrode was prepared by thermal compression of a negative electrode film on a Cu mesh in a 120 ℃ hot roll press.

An electrode slurry was prepared using 94% by weight of the cathode active material LiCoO ₂ according to the present invention, 3% by weight of a PVDF binder, and 3% by weight of a SPB (super P black) conductive material as a solvent. The prepared electrode slurry was applied to Al foil and dried to prepare a positive electrode.

A trielectrode pouch cell was prepared using a cathode and an anode (LiCoO ₂ ) coated on lithium and Cu mesh.

In the pretreatment process, lithium and the cathode (SiO-G) were reduced to 0V in a constant current process according to one process diagram shown in FIG. 2, followed by reduction treatment for 24 hours at 0V in a constant voltage process, followed by oxidation pretreatment to 3V. .

Figure 4 shows a graph showing the potential and current with respect to time when the silicon oxide and graphite composite electrode charged to 0V in a constant current process and then reduced pretreatment at 0V for 24 hours in a constant voltage process. Reduction pretreatment required 3252mAh / g, discharge pretreatment was 2177mAh / g, pretreatment coulombic efficiency 67% and pretreatment irreversible specific capacity 1075 mAh / g.

A charge and discharge test was conducted at a 0.1 C rate of the trielectrode battery subjected to the pretreatment.

Fig. 5 shows the results of this charge / discharge test and shows the potential and current with respect to time.

FIG. 6 shows specific amounts based on the weight of the negative electrode active material according to the cycle. In one cycle, the charge capacity was 752mAh / g and the discharge capacity was 730mAh / g, which showed an initial charge / discharge coulombic efficiency of 97%. In the second cycle, the charge capacity was 728mAh / g, the discharge capacity was 723mAh / g, and in the third cycle, the charge capacity was 718mAh / g and the discharge capacity was 711mAh / g, which showed a coulombic efficiency of 99%.

FIG. 7 shows specific amounts based on the weight of the positive electrode active material according to the cycle of FIG. 5. In one cycle, the charging and discharging capacity was 167mAh / g and the discharge capacity was 162mAh / g, indicating an initial charge / discharge coulombic efficiency of 97%. In the second cycle, the charge capacity was 132mAh / g, the discharge capacity was 160mAh / g, and in the third cycle, the charge capacity was 159mAh / g, and the discharge capacity was 158mAh / g, which showed a coulombic efficiency of 99%.

Table 1 summarizes the results of FIGS. 5, 6 and 7.

TABLE 1

        Cycle count characteristics Pretreatment process One 2 3 4 5 6 7 8 9  Cathode Specific Capacity Reduced Electricity (mAh / g) 3252 752 728 718 706 693 681 673 668 659 Oxidation amount (mAh / g) 2177 730 723 711 701 688 680 672 663 656 Coulomb Efficiency (%) 67 97 99 99 99 99 100 100 99 100 Irreversible specific capacity (mAh / g) 1075 22 5 7 5 4 One One 5 2 Cumulative irreversible specific capacity (mAh / g) 1075 1097 1102 1109 1114 1120 1121 1122 1126 1129 Anode Reference Specific Capacity Reduced Electricity (mAh / g) - 167 162 159 159 154 151 149 148 146 Oxidation amount (mAh / g) - 162 160 158 155 153 151 149 147 146 Coulomb Efficiency (%) - 97 99 99 99 99 100 100 99 100 Irreversible specific capacity (mAh / g) - 5 2 One 4 One 0 0 One One Cumulative irreversible specific capacity (mAh / g) - 5 7 8 12 10 10 10 11 12

As described above, it can be seen that the discharge (oxidation) specific amount can be stably represented from the initial stage by eliminating the irreversible specific amount in the initial charging and discharging by adopting the constant current-constant voltage process of the cathode.

1 is an example of configuration diagram of a rechargeable lithium battery according to one embodiment of the present invention;

2 is a manufacturing process diagram of a non-carbon-based material-based high-efficiency cathode according to an embodiment of the present invention,

3 is a manufacturing process diagram of a non-carbon-based material-based high-efficiency cathode according to an embodiment of the present invention,

Figure 4 is a graph showing the potential and current with respect to time when the silicon oxide and graphite composite negative electrode charged to 0V in a constant current process and then reduced pre-treatment at 0V for 24 hours in a constant voltage process, according to an embodiment of the present invention,

5 is a graph showing the results of the present charge / discharge test, showing the potential and current with respect to time;

FIG. 6 is a graph showing specific capacity based on the weight of the negative electrode active material according to the cycle of FIG. 5;

FIG. 7 is a graph showing specific capacity based on the weight of the positive electrode active material according to the cycle of FIG. 5.

** Description of the main symbols in the drawings *

전 reduction pretreatment electrolyzer

Oxidation pretreatment electrolyzer

㉢ cleaning tank

㉣ Drying tank

① Electrode plate

② Lithium counter electrode for reduction pretreatment

③ Organic electrolytic solution for reduction pretreatment

④ Lithium reference electrode for reduction pretreatment

⑤ Lithium counter electrode for oxidation pretreatment

⑥ Reference electrode for oxidation pretreatment

⑦ Electrode plate cleaning tank

⑧ Electrode Plate Drying Tank

Claims (8)

A negative electrode including a negative electrode active material, a binder, and a conductive material including a non-carbon compound including at least one of silicon oxide and tin oxide, and having an initial coulombic efficiency of 90% or more; LiCoO ₂ A positive electrode including a positive electrode active material; And Lithium secondary battery having an ion conductor. The lithium secondary battery of claim 1, wherein the negative electrode is obtained by performing a reduction pretreatment process. The lithium secondary battery according to claim 2, wherein the reduction pretreatment process is performed at a constant voltage of 0 V within a range of 1 to 60 hours after the voltage is set to 0 V through a constant current. The lithium secondary battery of claim 1, wherein the non-carbon-based compound is alloyed with graphite. The lithium secondary battery according to claim 4, wherein the mixing weight ratio of the non-carbon compound and graphite is in the range of 4: 6 to 6: 4. The lithium secondary battery of claim 1, wherein the silicon oxide has a range of x to 0.5 to 1.5 in SiO x. The lithium secondary battery of claim 1, wherein the silicon oxide has a range of x to 0.5 to 1.5 in SiO x. The lithium secondary battery according to any one of claims 1 to 7, wherein the lithium secondary battery is charged at a charging voltage in the range of 4.2 V to 4.5 V.

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