Composite for lithium ion metal hybrid battery anode and its manufacturing method

Abstract

The present invention relates to a composite for a lithium-ion metal hybrid battery negative electrode comprising carbon fibers and a cobalt-derived material formed on the surface of the carbon fibers, and a method for manufacturing the same. According to the present invention, the composite of the present invention can have improved lithium affinity properties to suppress lithium dendrite growth and simultaneously possess improved electrical properties, and the manufacturing method of the present invention can produce a composite for a lithium-ion metal hybrid battery negative electrode exhibiting high performance more quickly and simply through a Joule thermal process.

Description

Technology Field

[0001] The present invention relates to a composite for a lithium-ion metal hybrid battery negative electrode and a method for manufacturing the same, and more specifically, to a composite for a lithium-ion hybrid battery negative electrode in which lithium dendrite growth is suppressed and a method for manufacturing the same. Background Technology

[0002] Lithium-based batteries are utilized in numerous industrial sectors, ranging from portable electronic devices and electric vehicles to renewable energy storage systems, thanks to their excellent cost-effectiveness and energy storage capabilities. Nevertheless, as power consumption in electrical systems increases due to the rapid integration and interconnection of devices, existing lithium-based batteries face the challenge of improving performance for sustainable system operation. These challenges include addressing the low capacity, low voltage, and limited energy density of lithium-based batteries, as well as suppressing Li dendrite formation.

[0003] To address the aforementioned challenges, various strategies have emerged to hybridize lithium-ion and lithium-metal batteries by utilizing complementary energy storage mechanisms. Nevertheless, several challenges remain to further improve hybrid battery performance, particularly regarding the interface between the lithium metal layer and the cathode surface. The interface between the lithium metal layer and the cathode surface can significantly influence the uniformity and thickness of the lithium metal layer deposited on the cathode structure, the sequential interactions between charged lithium metal and lithium ions, and electrical impedance. Therefore, establishing a robust interface design between the lithium metal and the cathode is essential to further enhance the energy density and stability of hybrid batteries. The problem to be solved

[0004] The present invention is devised to solve the aforementioned problems and aims to disclose a composite for a lithium-ion metal hybrid battery negative electrode and a method for manufacturing the same, which can suppress the formation of Li dendrites on the negative electrode surface while simultaneously improving the capacity, voltage, and energy density of a lithium-based battery. means of solving the problem

[0005] The present invention discloses a composite for a lithium-ion metal hybrid battery negative electrode comprising a carbon fiber; and a cobalt-derived material formed on the surface of the carbon fiber, as a means to achieve the above-mentioned purpose.

[0006] Here, the above cobalt-derived material may include one or more materials selected from the group consisting of cobalt precursors, cobalt metal, and cobalt oxide.

[0007] Here, the cobalt oxide is formed by applying Joule thermal energy to the cobalt precursor and can be represented by the following chemical formula 1.

[0008] [Chemical Formula 1]

[0009] Co x O y

[0010] Here, x is a real number from 1 to 3, and y is a real number from 1 to 4.

[0011] Here, the cobalt oxide represented by Co2O3 may be included in a fraction of 20 to 100% with respect to the cobalt-derived material.

[0012] Here, the diameter of the carbon fiber may be 0.5 nm to 15 µm.

[0013] In addition, the present invention discloses a method for manufacturing a composite for a lithium-ion metal hybrid battery negative electrode, comprising the steps of: coating a cobalt precursor solution on the surface of a carbon fiber to achieve the above-described objective; applying Joule-heating energy to the coated carbon fiber to manufacture a cobalt-derived material / carbon fiber electrode; and washing the manufactured cobalt-derived material / carbon fiber electrode.

[0014] Here, the cobalt precursor solution may include one or more cobalt precursors selected from the group consisting of cobalt nitrate, cobalt acetate, cobalt sulfate, cobalt chloride, and cobalt bromide.

[0015] Here, the cobalt precursor solution coated on the surface of the carbon fiber can form cobalt oxide as Joule thermal energy is applied.

[0016] Here, the power of the above Joule heat energy can be 150 to 250 W.

[0017] Here, the duration of the above Joule heat energy may be 0.3 to 0.6 s.

[0018] Here, the washing step may be performed using one or more solvents selected from the group consisting of water, ethanol, diethyl ether, methanol, ammonia, acetone, dimethyl sulfoxide, n-butanol, and butanediol.

[0019] In addition, the present invention discloses a lithium-ion metal hybrid battery comprising the above-described composite for a lithium-ion metal hybrid battery negative electrode as a means to achieve the above-described purpose. Effects of the invention

[0020] The composite for the negative electrode of the lithium-ion metal hybrid battery of the present invention has improved lithium affinity characteristics, which suppress lithium dendrite growth, and can simultaneously have improved electrical characteristics.

[0021] In addition, the method for manufacturing a lithium-ion metal hybrid battery negative electrode composite of the present invention can manufacture a lithium-ion metal hybrid battery negative electrode composite exhibiting high performance more quickly and simply through a Joule thermal process. Brief explanation of the drawing

[0022] FIG. 1 is a schematic diagram illustrating a composite for a lithium-ion metal hybrid battery negative electrode according to the present invention. FIG. 2 is a schematic diagram illustrating the lithiation process in a cathode comprising a composite for a lithium-ion metal hybrid battery cathode according to one embodiment of the present invention. Figure 3 is a flowchart illustrating the manufacturing process of a composite for a lithium-ion metal hybrid battery negative electrode according to the present invention. Figure 4 is a graph showing the temperature profile according to the power magnitude in the Joule thermal process of the present invention. Figure 5 is an SEM image of a composite for a lithium-ion metal hybrid battery negative electrode manufactured when the power size in the Joule thermal process of the present invention is set to 300 W. Figure 6 is an SEM image of a composite for a lithium-ion metal hybrid battery negative electrode manufactured according to one embodiment of the present invention. Figure 7 is an XRD spectrum of a composite for a lithium-ion metal hybrid battery negative electrode manufactured according to one embodiment of the present invention. Figure 8 is an XRD spectrum of a composite for a lithium-ion metal hybrid battery negative electrode manufactured according to one embodiment of the present invention. FIG. 9 is a graph showing the fraction of Co-derived molecules in a composite for a lithium-ion metal hybrid battery negative electrode manufactured according to one embodiment of the present invention. FIG. 10 is a graph showing the percentage of carbon atoms according to the lithiation process of a composite for a lithium-ion metal hybrid battery negative electrode manufactured according to one embodiment of the present invention. FIG. 11 is a graph showing the charging curve and nucleation overvoltage trend during the initial lithiation process of a lithium-ion metal hybrid battery (half-cell) according to one embodiment of the present invention. FIG. 12 is a Coulomb efficiency profile of a lithium-ion metal hybrid battery (half-cell) according to one embodiment of the present invention. FIG. 13 is a Coulomb efficiency profile of a lithium-ion metal hybrid battery (full-cell) according to one embodiment of the present invention. FIG. 14 is a graph showing the energy density of a lithium-ion metal hybrid battery (full-cell) according to one embodiment of the present invention. FIG. 15 is a graph comparing the number of cycles until the cutoff voltage (2 V) of a lithium-ion metal hybrid battery (full-cell) according to one embodiment of the present invention is reached. Specific details for implementing the invention

[0023] The present invention is capable of various modifications and may have various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the invention to specific embodiments, and it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0024] Throughout this specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0025] As used herein, terms of degree such as “about,” “substantially,” etc., are used to mean at or near the stated value when inherent manufacturing material tolerances are presented in the said sense, and are used to prevent unscrupulous infringers from unfairly exploiting the disclosed content in which precise or absolute values ​​are mentioned to aid in understanding the invention. Furthermore, throughout this specification, “a step of” or “a step of” does not mean “a step for”.

[0026] Since a person skilled in the art can make various applications through the gist of the present invention, the scope of the rights of the present invention is not limited to the following embodiments. The scope of the rights of the present invention extends to parts that are obvious to a person skilled in the art who can easily substitute or modify using prior art based on the matters described in the specific claims.

[0027] The present invention will be described in more detail below with reference to the attached drawings, where necessary.

[0029] <Composite for Lithium-Ion Metal Hybrid Battery Anode>

[0030] The present invention discloses a composite for a lithium-ion metal hybrid battery negative electrode comprising a carbon fiber; and a cobalt-derived material formed on the surface of the carbon fiber, as a means to achieve the above-mentioned purpose.

[0031] The above cobalt-derived material may include one or more materials selected from the group consisting of cobalt precursors, cobalt metal, and cobalt oxide.

[0032] Here, the cobalt oxide is formed by applying Joule thermal energy to the cobalt precursor and can be represented by the following chemical formula 1.

[0033] [Chemical Formula 1]

[0034] Co x Oy

[0035] Here, it is preferable that x is a real number from 1 to 3 and y is a real number from 1 to 4, and more preferable that x is a real number from 2 to 3 and y is a real number from 3 to 4.

[0036] More specifically, the form of the above cobalt oxide may be at least one of CoO, Co2O3, and Co3O4. A more preferred form of the cobalt oxide may be Co2O3 or Co3O4. As will be explained in more detail below, the cobalt precursor coated on the surface of the carbon fiber may be oxidized from the above cobalt precursor to a cobalt oxide through a process of applying Joule thermal energy (hereinafter referred to as the "Joule thermal process"). However, among the above cobalt oxides, CoO is a form reduced by additionally applied Joule thermal energy after the above cobalt precursor has been oxidized and converted into Co2O3 or Co3O4. Accordingly, in the present invention, a preferred form of the above cobalt oxide may be Co2O3 or Co3O4.

[0037] In addition, the composite of the present invention may include cobalt metal, which is the final reduced form of the cobalt precursor. However, since an increase in the content of the cobalt metal may lead to a decrease in the lithium affinity characteristics of the composite of the present invention derived from the cobalt oxide, it is preferable that the content of the cobalt metal be less than 10% of the total cobalt-derived materials (cobalt precursor, cobalt metal, and cobalt oxide), and most preferable that it not be included.

[0038] Here, it is preferable that the cobalt oxide represented by Co2O3 be included in a fraction of 20 to 100% with respect to the cobalt-derived material. If the cobalt oxide represented by Co2O3 is included in a fraction of less than 20%, it is difficult to impart lithium-affinity characteristics to the composite of the present invention, and thus a problem may arise in which the performance of the lithium-ion metal hybrid battery containing the composite of the present invention is degraded.

[0039] Here, the diameter of the carbon fiber is preferably 0.5 nm to 15 μm, and more preferably 1 to 15 μm. That is, in the present invention, carbon nanotubes with a diameter of 0.5 to 100 nm may be used as the carbon fiber, and carbon fibers with a diameter of 100 nm to 15 μm may also be used. However, if carbon nanotubes with a diameter of 0.5 to 100 nm are used as the carbon fiber of the present invention, a problem of increased process costs may occur. In addition, if the diameter of the carbon fiber exceeds 15 μm, a problem of reduced lithium affinity characteristics originating from the cobalt-derived material may occur. Accordingly, in the present invention, the diameter of the carbon fiber is preferably 0.5 nm to 15 μm.

[0040] FIG. 1 is a schematic diagram illustrating a composite for a lithium-ion metal hybrid battery negative electrode according to the present invention. More specifically, FIG. 1a is a schematic diagram of a composite for a lithium-ion metal hybrid battery negative electrode according to the present invention, FIG. 1b is a schematic diagram illustrating the appearance of the composite for a lithium-ion metal hybrid battery negative electrode according to the present invention during initial lithiation, and FIG. 1c is a schematic diagram illustrating the appearance of the composite for a lithium-ion metal hybrid battery negative electrode according to the present invention during lithium coating after the lithiation process.

[0041] Referring to FIG. 1, it can be seen that the composite for a lithium-ion metal hybrid battery negative electrode of the present invention can achieve excellent lithiation and Li-plated characteristics when the composite is utilized as a negative electrode, as cobalt oxide particles with a high oxidation state are strongly fixed to the surface of carbon fibers. When current is applied to a negative electrode containing an electrolyte containing Li ions and the composite of the present invention, sufficient Li ions can be preferentially intercalated between carbon atoms and the carbon fiber interface, and furthermore, can be stored in the cobalt oxide particles due to their unique lithiation characteristics. Consequently, the formation of lithium dendrites is suppressed due to the lithium affinity of the cobalt oxide particles, and Li metal can be uniformly deposited on the surface of the composite of the present invention.

[0042] Furthermore, the present invention may utilize the carbon fiber in a woven form. In the present invention, by using the woven carbon fiber, not only can the convenience of the process for manufacturing the composite of the present invention be expected to be increased, but the effect of increasing the specific surface area of ​​the carbon fiber can also be achieved. When the specific surface area of ​​the carbon fiber increases, the lithium ion storage capacity can be increased, and consequently, the performance of the lithium-ion metal hybrid battery can be expected to be improved.

[0043] The thickness of the woven carbon fiber is preferably 10 to 500 μm, and more preferably 200 to 400 μm.

[0044] FIG. 2 is a schematic diagram illustrating the lithiation process in a cathode comprising a composite for a lithium-ion metal hybrid battery cathode according to one embodiment of the present invention. More specifically, FIG. 2 illustrates the lithiation process of a Cu cathode, a carbon cathode, and the composite for a lithium-ion metal hybrid battery cathode of the present invention, respectively.

[0045] Referring to FIG. 2, the lithiation process at each cathode is described as follows. First, in the case of a Cu cathode, active interaction with the electrolyte containing Li ions is limited due to the small surface area, and the inherent properties of the material may hinder the storage of a sufficient amount of Li ions. This can reduce the lithiation capability, which is an important function of lithium-based batteries. Additionally, the lithium-incompatible characteristics of the Cu cathode can result in an uneven and rough surface and a thin Li coating. Next, the carbon cathode can achieve significant lithiation due to its large surface area and high porosity, which allows it to store a large amount of Li ions. However, the carbon cathode also has lithium-incompatible characteristics, which may also hinder the achievement of appropriate Li coating performance. In contrast, the cathode comprising the composite of the present invention can promote not only powerful lithiation but also a uniform and thick Li coating function as the combination of a large surface area, high porosity, and lithium-compatible characteristics is achieved. That is, Cu cathodes and carbon cathodes have the disadvantages of dendrite growth that reduces the stability of charge discharge cycles and low capacity that reduces energy density, but in the case of the composite of the present invention, dendrites are suppressed and high capacity is achieved at the same time, thereby ensuring cycle stability and high energy density of the lithium-ion metal hybrid battery.

[0047] Method for manufacturing a composite for a lithium-ion metal hybrid battery cathode

[0048] In addition, the present invention discloses a method for manufacturing a composite for a lithium-ion metal hybrid battery negative electrode as a means to achieve the above-mentioned purpose.

[0049] Figure 3 is a flowchart illustrating the manufacturing process of a composite for a lithium-ion metal hybrid battery negative electrode according to the present invention.

[0050] Referring to FIG. 3, it can be seen that the method for manufacturing a composite for a lithium-ion metal hybrid battery negative electrode according to the present invention comprises the steps of: coating a cobalt precursor solution on the surface of a carbon fiber; applying Joule-heating energy to the coated carbon fiber to manufacture a cobalt-derived material / carbon fiber electrode; and washing the manufactured cobalt-derived material / carbon fiber electrode.

[0051] The above cobalt precursor can be oxidized to form cobalt oxide as Joule thermal energy is applied.

[0052] Here, the cobalt precursor solution may comprise one or more cobalt precursors selected from the group consisting of cobalt nitrate, cobalt acetate, cobalt sulfate, cobalt chloride, and cobalt bromide, but is not limited thereto.

[0053] Here, it is preferable that the power of the above Joule thermal energy be 150 to 250 W. If the power of the above Joule thermal energy is less than 150 W, it is difficult to completely decompose the precursor within a short period of time, which may result in a problem where a sufficient amount of cobalt oxide is not formed. On the other hand, if the power of the above Joule thermal energy exceeds 250 W, cobalt metal / cobalt oxide (hereinafter referred to as "Co / Co") x O y Aggregation of (which may occur) may take place, and a problem may arise in which damage to the carbon fiber substrate occurs.

[0054] Figure 4 is a graph showing the temperature profile according to the power magnitude in the Joule thermal process of the present invention.

[0055] Referring to Fig. 4, it can be confirmed that a high-temperature environment is created within a short time by the Joule heating process, enabling rapid synthesis of the composite of the present invention. Specifically, it can be observed that a temperature exceeding 500 K is first detected after 100 W of Joule heating energy is applied for 0.8 seconds, and increases to 1131 K when heated for 2 seconds. However, considering that the decomposition temperature range of the cobalt precursor is 450 to 520 K, a problem may arise where it is difficult to completely decompose the precursor within a short time with 100 W of power. In contrast, when the power is 200 W, it can be observed that the temperature exceeds 500 K when the duration is 0.3 seconds, and rapidly rises to 1322 K within 0.8 seconds. Furthermore, if additional oxygen is introduced during the Joule heating process, the precursor can be immediately decomposed and simultaneously converted into Co metal and Co oxide as shown in the following reaction equation.

[0056] [Reaction Equation 1]

[0057] Co(NO3)2(s) → Co x O y (s) + NO z (g) + O2(g)

[0058] Finally, when the Joule thermal power was 300 W, temperatures above 500 K were observed within a duration of 0.1 s, and it was confirmed that the temperature rapidly reached 1505 K within a duration of 0.8 s. However, while the condition of 300 W Joule thermal power can apply sufficient energy to the sample for the decomposition of the cobalt precursor and Co oxidation, if a high-energy-density electric shock is applied suddenly, Co / Co x O y Problems resulting in severe particle aggregation and damage to the carbon fiber substrate may occur.

[0059] FIG. 5 is an SEM image of a composite for a lithium-ion metal hybrid battery negative electrode manufactured when the power magnitude in the Joule thermal process of the present invention is 300 W. More specifically, FIG. 5a is an SEM image of the composite when the duration is 0.2 s, FIG. 5b is an SEM image of the composite when the duration is 0.4 s, FIG. 5c is an SEM image of the composite when the duration is 0.6 s, and FIG. 5d is an SEM image of the composite when the duration is 0.8 s.

[0060] Referring to FIG. 5, as the power magnitude in the Joule heating process is set to 300 W, Co / Co even with a short duration of 0.2 s x O y The aggregation of particles can be observed, and furthermore, from the point where the duration is 0.6 s, the carbon fiber is damaged, and Co / Co to the damaged part of the carbon fiber x O y You can see the particles have penetrated.

[0061] Here, it is preferable that the duration of the Joule heat energy is 0.3 to 0.6 s. If the duration of the Joule heat energy is less than 0.3 s, the decomposition of the cobalt precursor does not occur sufficiently, which may lead to a problem where cobalt oxide is not sufficiently formed. On the other hand, if the duration of the Joule heat energy exceeds 0.6 s, Co / Co x O y Aggregation may occur, and problems may arise that result in damage to the carbon fiber substrate. This will be explained in more detail in the following {Examples and Evaluation} section.

[0062] Here, the applied Joule heat energy is more specifically 30 to 65 J / cm² 2 It is desirable.

[0063] Here, the washing step may be performed using one or more solvents selected from the group consisting of water, ethanol, diethyl ether, methanol, ammonia, acetone, dimethyl sulfoxide, n-butanol, and butanediol. In the manufacturing method of the present invention, by washing the manufactured cobalt-derived material / carbon fiber electrode with the above solvent, excess cobalt precursor can be removed, and consequently, the effect of securing the specific surface area of ​​the cobalt-derived material / carbon fiber electrode can be achieved.

[0065] Lithium-ion Metal Hybrid Battery

[0066] In addition, the present invention discloses a lithium-ion metal hybrid battery comprising the above-described composite for a lithium-ion metal hybrid battery negative electrode as a means to achieve the above-described purpose.

[0067] The composite of the present invention can be used as a negative electrode of a lithium-ion metal hybrid battery. Furthermore, the composite of the present invention included in the lithium-ion metal hybrid battery may be coated with lithium metal on its surface through a lithiation process. As a cobalt-derived material is formed on the surface of the composite of the present invention, the active surface area for electrochemical reactions may be increased, and as a result, durability may be improved by preventing the delamination of the active material. Moreover, the interfacial conductivity of the composite of the present invention may be improved by including carbon fibers that provide additional charge transfer pathways.

[0068] When an electric current is applied between an electrolyte containing lithium ions and a cathode containing the composite of the present invention, sufficient lithium ions Co / Co x O y Not only is it stored in the particles, but it can also be preferentially intercalated between the layers of carbon atoms in the carbon fibers. As a result, lithium metal is Co / Co x O yDue to the lithium affinity of the particles, they can be uniformly deposited on the surface of carbon fibers, and dendrite formation can be suppressed.

[0069] The lithium-ion metal hybrid battery of the present invention includes the above-described composite as a negative electrode, thereby suppressing the growth of lithium dendrites and achieving a maximum energy density of 272.59 Wh / kg, which can be maintained stably without a significant decrease in energy density during more than 110 charge-discharge cycles.

[0071] Hereinafter, the claims of this specification will be explained in more detail with reference to the attached drawings and embodiments. However, as the drawings and embodiments presented in this specification may be modified in various ways by a person skilled in the art and may take various forms, the details described in this invention should not be limited to a specific disclosed form, but should be understood to include all equivalents and substitutions included within the spirit and technical scope of this invention. Furthermore, the attached drawings are presented to help a person skilled in the art understand the invention more accurately and may be depicted in an exaggerated or reduced size compared to the actual size.

[0073] {Examples and Evaluation}

[0074] <Example>

[0075] Example 1

[0076] First, cobalt(II) nitrate hexahydrate (Co(NO3)2-6H2O) was dissolved in ethanol at a concentration of 1 M. 75 µl of the above solution was drop-cast onto porous graphite (hereinafter referred to as pG) with a film thickness of 330 µm, and then dried at room temperature for 1 hour. The pG coated with the cobalt precursor was coupled with an electric clamp combined with a Joule thermal processing device (ITECK ELECTRONICS, IT6512D, ≤0.05% + 30 mV, ≤0.2% + 120 mA), and Joule thermal energy was applied. At this time, the power of the Joule thermal energy was 200 W, and the duration was 0.3 s. The composite thus prepared was cooled at room temperature for 10 times the duration, washed with deionized water, and then dried in a vacuum chamber at a temperature of 60 ℃ for 24 hours (hereinafter referred to as "Example 1").

[0078] Example 2

[0079] A composite for a lithium-ion metal hybrid battery negative electrode was prepared in the same manner as in Example 1, except that the Joule heat energy duration was set to 0.4 s (hereinafter referred to as "Example 2").

[0081] Example 3

[0082] A composite for a lithium-ion metal hybrid battery negative electrode was prepared in the same manner as in Example 1, except that the Joule heat energy duration was set to 0.5 s (hereinafter referred to as "Example 3").

[0084] Example 4

[0085] A composite for a lithium-ion metal hybrid battery negative electrode was prepared in the same manner as in Example 1, except that the Joule heat energy duration was set to 0.6 s (hereinafter referred to as "Example 4").

[0087] Comparative Example 1

[0088] A copper plate with a thickness of 330 μm was manufactured by depositing copper on a substrate (hereinafter referred to as "Comparative Example 1").

[0090] Comparative Example 2

[0091] A porous graphite (hereinafter referred to as pG) with a film thickness of 330 μm was prepared (hereinafter referred to as "Comparative Example 2").

[0093] Comparative Example 3

[0094] A composite for a lithium-ion metal hybrid battery negative electrode was prepared in the same manner as in Example 1, except that the Joule heat energy duration was set to 0.1 s (hereinafter referred to as "Comparative Example 3").

[0096] Comparative Example 4

[0097] A composite for a lithium-ion metal hybrid battery negative electrode was prepared in the same manner as in Example 1, except that the Joule heat energy duration was set to 0.2 s (hereinafter referred to as "Comparative Example 4").

[0099] Comparative Example 5

[0100] A composite for a lithium-ion metal hybrid battery negative electrode was prepared in the same manner as in Example 1, except that the Joule heat energy duration was 0.7 s (hereinafter referred to as "Comparative Example 5").

[0102] Comparative Example 6

[0103] A composite for a lithium-ion metal hybrid battery negative electrode was prepared in the same manner as in Example 1, except that the Joule heat energy duration was set to 0.8 s (hereinafter referred to as "Comparative Example 6").

[0105] <Evaluation>

[0106] FIG. 6 is an SEM image of a composite for a lithium-ion metal hybrid battery negative electrode prepared according to one embodiment of the present invention. More specifically, FIG. 6a is an SEM image of Comparative Example 3, FIG. 6b is an SEM image of Comparative Example 4, FIG. 6c is an SEM image of Example 1, FIG. 6d is an SEM image of Example 2, FIG. 6e is an SEM image of Example 3, FIG. 6f is an SEM image of Example 4, FIG. 6g is an SEM image of Comparative Example 5, and FIG. 6h is an SEM image of Comparative Example 6.

[0107] Referring to FIG. 6, in the case of Comparative Examples 3 and 4, it can be seen that undecomposed cobalt precursors still remain due to the short duration of Joule thermal energy application, and that cobalt oxide was not sufficiently formed. In contrast, in the case of Examples 1 to 3, Co / Co x O y It can be observed that the particles are well distributed. From Example 4 onwards, Co / Co x O y It can be observed that particle aggregation begins to occur, and in the case of Comparative Examples 5 and 6, as defects in the carbon fibers occur, the above Co / Co x O y It can be observed that the particles have penetrated into the defects of the carbon fibers.

[0108] FIG. 7 is an XRD spectrum of a composite for a lithium-ion metal hybrid battery negative electrode prepared according to one embodiment of the present invention. More specifically, FIG. 7a is an XRD spectrum of Comparative Example 4, Example 2, and Example 4, and FIG. 7b is an XRD spectrum of Example 4 and Comparative Example 5.

[0109] When comparing the XRD spectra of the example and the comparative example with reference to FIG. 7, Co2O3(2 It can be confirmed that the most distinct peak corresponding to (2θ = 36.9°) exhibits the highest intensity in Example 2. Additionally, referring to the XRD spectrum of Comparative Example 4, it can be seen that the peak corresponding to Co2O3 (2θ = 36.9°) appears broadly with low intensity because a sufficient amount of cobalt oxide is not formed due to the short duration of Joule thermal energy application. Furthermore, comparing the XRD spectra of Example 4 and Comparative Example 5, it can be seen that as the duration of Joule thermal energy application increases from 0.6 s to 0.7 s, defects in the carbon fiber occur, and as a result, the carbon-related XRD peak value (2θ) shifts from 25.64° to 26.24°.

[0110] Figure 8 is an XRD spectrum of a composite for a lithium-ion metal hybrid battery negative electrode manufactured according to one embodiment of the present invention.

[0111] Referring to Fig. 8, it can be seen that in Comparative Example 3, sufficient Joule thermal energy was not transferred to the cobalt precursor, so the state of the cobalt precursor still remains. In the case of Comparative Example 4, peaks related to Co2O3 and Co3O4 began to be observed, but it can be seen that the cobalt precursor still remains. Furthermore, as confirmed in Fig. 7, the most distinct peak corresponding to Co2O3 (2θ = 36.9°) shows the highest intensity in Example 2. Up to Example 2, the cobalt precursor shows a tendency to oxidize, but from Example 3 onwards, it shows a gradual tendency to reduce. Supporting this, the XRD peak of Example 3 shows a peak corresponding to CoO. Moreover, from Comparative Example 5, it can be seen that the peak corresponding to Co2O3 disappears and the peak corresponding to cobalt metal begins to increase.

[0112] FIG. 9 is a graph showing the fraction of Co-derived molecules in a composite for a lithium-ion metal hybrid battery negative electrode prepared according to one embodiment of the present invention. FIG. 9 shows the fraction of Co-derived molecules based on the XPS spectra of each embodiment and comparative example analyzed in FIG. 8.

[0113] Referring to FIG. 9, as described in FIG. 8, it can be confirmed that in Comparative Examples 3 and 4, the cobalt precursor remains, and the fraction of the cobalt precursor accounts for a significant portion of the total Co-derived molecule. In contrast, in Examples 1 to 4, it can be confirmed that there is no fraction occupied by the cobalt precursor, and that cobalt oxides represented by CoO, Co2O3, and Co3O4 account for the majority. However, starting from Example 3, a reducing trend is gradually exhibited, and the XRD peak of Example 3 shows an increase in the fraction corresponding to CoO. Furthermore, starting from Comparative Example 5, it can be confirmed that the fraction corresponding to Co2O3 disappears and the fraction corresponding to cobalt metal begins to increase. That is, from the results described above, in the present invention, Co / Co x O y The minimum Joule heat energy application time required for a complete conversion is 0.3 s, which is 31.3 J / cm². 2 It can be inferred that it is.

[0114] FIG. 10 is a graph showing the percentage of carbon atoms according to the lithiation process of a composite for a lithium-ion metal hybrid battery negative electrode manufactured according to an embodiment of the present invention. (i) to (v) shown in FIG. 10 represent each stage of the charge-discharge process, and specifically, stage (i) is the initial lithiation stage, and (ii) is 1 mA / cm² 2 3 mAh / cm² under a constant current density 2 Li coating step of capacity, (iii) is 1 mA / cm² 2 4 mAh / cm² under a constant current density2 The Li coating step of the capacity, (iv) is 1 mA / cm² 2 5 mAh / cm² under a constant current density 2 The Li coating step of the capacity, (v) means the delithiation step.

[0115] Referring to FIG. 10, in the case of Comparative Example 2, the percentage of carbon atoms was approximately 80% in the initial stage of lithiation, but as current was applied, a large amount of lithium ions were deposited on the surface, and it can be seen that the percentage of carbon atoms in stage (iv) decreased to approximately 40%. In contrast, in the case of Example 2, it can be seen that the percentage of carbon atoms was approximately 60% due to the cobalt oxide formed on the surface of the carbon fiber in the initial stage of lithiation. Furthermore, in the case of Example 2, the lithium affinity is enhanced due to the cobalt oxide formed on the surface of the carbon fiber, and as the lithium coating formed from the inside of the composite of Example 2 upon current application, it can be seen that the percentage of carbon atoms was approximately 53% in stages (iii) - (iv). That is, the above results suggest that the composite for the negative electrode of the lithium-ion metal hybrid battery of the present invention can store a larger amount of lithium ions compared to a bare carbon fiber electrode.

[0116] FIG. 11 is a graph showing the charging curve and nucleation overvoltage trend during the initial lithiation process of a lithium-ion metal hybrid battery (half-cell) according to one embodiment of the present invention. More specifically, FIG. 11a shows the charging curve during the initial lithiation process of a lithium-ion metal hybrid battery (half-cell) including Comparative Example 1, Comparative Example 2, and Example 2, and FIG. 11b is a graph showing the nucleation overvoltage trend of a lithium-ion metal hybrid battery (half-cell) including Comparative Example 1, Comparative Example 2, and Example 2.

[0117] Referring to FIG. 11a, it can be seen that the half-cell containing Comparative Example 1 as the cathode relies primarily on lithium metal during the charging cycle over the entire capacity range. In contrast, for the half-cell containing Comparative Example 2 as the cathode and the half-cell containing Example 2 as the cathode, the capacity is approximately 2 mAh / cm². 2 Based on the capacity, it can be confirmed that lithium metal and lithium ions sequentially participate in the charge-discharge process. In addition, to evaluate stability according to charging speed, 1 ~ 10 mA / cm 2 Nucleation overpotential was measured at a current density within a range. A larger overpotential value indicates that dendrites are formed more effectively. Referring to Fig. 11b, it can be seen that as the charging speed increases, the overpotential values ​​of the half-cells containing Comparative Example 1 and Comparative Example 2 as the cathode increase significantly from 93 mV and 26 mV to 412 mV and 183 mV, respectively, while the half-cell containing Example 2 as the cathode maintains a stable level from 28 mV to 60 mV.

[0118] FIG. 12 is a Coulomb efficiency profile of a lithium-ion metal hybrid battery (half-cell) according to one embodiment of the present invention. More specifically, FIG. 12a is 4 mAh / cm² 2 capacitance of, 1 mA / cm² 2 This is the Coulomb efficiency profile at a current density of , and FIG. 12b is 4 mAh / cm 2 capacitance of, 2 mA / cm² 2 This is the Coulomb efficiency profile at a current density of , and FIG. 12c is 4 mAh / cm² 2 capacitance of, 5 mA / cm² 2 This is the Coulomb efficiency profile at a current density of , and FIG. 12d is 4 mAh / cm 2 capacitance, 10 mA / cm² 2 This is the Coulomb efficiency profile at a current density of .

[0119] Referring to Fig. 12, the current density is 1 to 2 mA / cm² 2 It can be confirmed that at a low charge discharge rate, the half-cell containing Example 2 exhibits continuous stability for more than 90 cycles, whereas the half-cells containing Comparative Example 1 and Comparative Example 2 exhibit critical performance degradation after only 13 and 45 cycles, respectively. Additionally, at a current density of 5 to 10 mA / cm² 2 Even in the high current test, the half-cell containing Example 2, unlike the half-cells containing Comparative Examples 1 and 2, shows 5 mA / cm 2 At 45 cycles, 10 mA / cm 2 It can be confirmed that it exhibits stability lasting for more than 30 cycles. These results suggest that the cathode using the composite for the lithium-ion metal hybrid battery cathode of the present invention can improve not only cyclic stability but also Coulomb efficiency, and based on this, it can contribute to significantly improving the performance of the lithium-ion metal hybrid battery.

[0120] FIG. 13 is a Coulomb efficiency profile of a lithium-ion metal hybrid battery (full-cell) according to one embodiment of the present invention. More specifically, FIG. 13a is a Coulomb efficiency profile of a full-cell designed with an N / P ratio of 0.8, and FIG. 13b is a Coulomb efficiency profile of a full-cell designed with an N / P ratio of 1.0. The capacitance was 177 mAh / g, and the current was 0.20 C.

[0121] Referring to FIG. 13, it can be seen that in the case of a full cell containing Comparative Example 1 as the cathode, the discharge capacity decreased significantly from 50.63 mAh / g in 2 cycles to 4.98 mAh / g in 9 cycles. This performance degradation is attributed to the limited lithiation and Li coating capacity of Comparative Example 1. Additionally, in the case of a full cell containing Comparative Example 2 as the cathode, it can be seen that the discharge capacity decreased sharply from 166.44 mAh / g to 100.71 mAh / g over 60 cycles. In contrast, in the case of a full cell containing Example 2 as the cathode, it can be seen that the discharge capacity remained stable from 173.87 mAh / g to 148.60 mAh / g over 110 cycles. Meanwhile, in the case of a full cell designed with an N / P ratio of 1.0 (current = 0.25 C), it can be confirmed that both Comparative Example 2 and Example 2, which are included as the cathode, achieve a stable discharge capacity for more than 160 cycles.

[0122] FIG. 14 is a graph showing the energy density of a lithium-ion metal hybrid battery (full-cell) according to one embodiment of the present invention.

[0123] Referring to FIG. 14, in the case of a full cell designed with an N / P ratio of 1.0 (current = 0.25 C), it can be seen that both the full cell containing Comparative Example 2 and Example 2 as the cathode achieve a stable energy density (228.31 Wh / kg and 229.64 Wh / kg, respectively) for more than 160 cycles. However, in the case of a full cell designed with a current of 0.20 C and an N / P ratio of 0.8 (current = 0.20 C), the energy density of the full cell containing Comparative Example 2 as the cathode decreased from 264.79 Wh / kg to 156.88 Wh / kg over 60 cycles, whereas the full cell containing Example 2 as the cathode achieved a high energy density of 272.59 Wh / kg and maintained a constant level for more than 110 cycles.

[0124] That is, from the results shown in FIGS. 13 and 14, it can be inferred that the composite for a lithium-ion metal hybrid battery negative electrode of the present invention can significantly improve the energy density and cyclic stability of a lithium-ion metal hybrid battery containing it, based on excellent lithium ionization and lithium coating performance.

[0125] FIG. 15 is a graph comparing the number of cycles until a cutoff voltage (2 V) is reached for a lithium-ion metal hybrid battery (full-cell) according to one embodiment of the present invention. More specifically, FIG. 15a compares the number of cycles until a cutoff voltage (2 V) is reached for a full cell including Comparative Example 2 and Example 2 as the negative electrode, and FIG. 15b compares the number of cycles until a cutoff voltage (2 V) is reached for a full cell including Examples 1 to 4 and Comparative Examples 4 to 6 as the negative electrode.

[0126] Referring to FIG. 15, it can be seen that a full cell containing Comparative Example 2 and Example 6 as the cathode reaches a cutoff voltage of 2 V at approximately 6 cycles or less. In contrast, in the case of Examples 1 to 4, it can be seen that a cutoff voltage of 2 V is reached at approximately 20 cycles or more.

[0127] The composite for the negative electrode of the lithium-ion metal hybrid battery of the present invention has improved lithium affinity characteristics, which suppress lithium dendrite growth, and can simultaneously have improved electrical characteristics.

[0128] In addition, the method for manufacturing a lithium-ion metal hybrid battery negative electrode composite of the present invention can manufacture a lithium-ion metal hybrid battery negative electrode composite exhibiting high performance more quickly and simply through a Joule thermal process.

[0129] The above description is merely an illustrative explanation of the technical concept of the present invention, and those skilled in the art to which the present invention pertains will be able to make various modifications and variations within the scope of the essential characteristics of the present invention.

[0130] Accordingly, the embodiments disclosed in this invention are intended to illustrate, not limit, the technical concept of the invention, and the scope of the technical concept of the invention is not limited by these embodiments. The scope of protection of this invention shall be interpreted by the claims below, and all technical concepts within an equivalent scope shall be interpreted as being included within the scope of rights of this invention.

Claims

Claim 1 A composite for a lithium-ion metal hybrid battery negative electrode comprising: a carbon fiber; and a cobalt-derived material formed on the surface of the carbon fiber, wherein the cobalt-derived material comprises one or more materials selected from the group consisting of a cobalt precursor, a cobalt metal, and a cobalt oxide, and wherein the cobalt oxide represented by Co2O3 is included in a fraction of 20 to 100% with respect to the cobalt-derived material. Claim 2 A composite for a lithium-ion metal hybrid battery negative electrode according to claim 1, wherein the cobalt oxide is formed by applying Joule thermal energy to the cobalt precursor. Claim 3 A composite for a lithium-ion metal hybrid battery negative electrode according to claim 1, wherein the diameter of the carbon fiber is 0.5 nm to 15 μm. Claim 4 A method for manufacturing a composite for a lithium-ion metal hybrid battery negative electrode, comprising: a step of coating a cobalt precursor solution onto the surface of a carbon fiber; a step of applying Joule-heating energy to the coated carbon fiber to manufacture a cobalt-derived material / carbon fiber electrode; and a step of washing the manufactured cobalt-derived material / carbon fiber electrode; wherein the cobalt-derived material comprises one or more materials selected from the group consisting of a cobalt precursor, cobalt metal, and cobalt oxide, and the cobalt oxide represented by Co2O3 is included in a fraction of 20 to 100% with respect to the cobalt-derived material. Claim 5 A method for manufacturing a composite for a lithium-ion metal hybrid battery negative electrode according to claim 4, wherein the cobalt precursor solution comprises one or more cobalt precursors selected from the group consisting of cobalt nitrate, cobalt acetate, cobalt sulfate, cobalt chloride, and cobalt bromide. Claim 6 A method for manufacturing a composite for a lithium-ion metal hybrid battery negative electrode according to claim 4, wherein the cobalt precursor solution coated on the surface of the carbon fiber forms cobalt oxide when Joule thermal energy is applied. Claim 7 A method for manufacturing a composite for a lithium-ion metal hybrid battery negative electrode according to claim 4, wherein the power of the Joule thermal energy is 150 to 250 W. Claim 8 A method for manufacturing a composite for a lithium-ion metal hybrid battery negative electrode according to claim 4, wherein the duration of the Joule thermal energy is 0.3 to 0.6 s. Claim 9 A method for manufacturing a composite for a lithium-ion metal hybrid battery negative electrode according to claim 4, wherein the washing step is performed using one or more solvents selected from the group consisting of water, ethanol, diethyl ether, methanol, ammonia, acetone, dimethyl sulfoxide, n-butanol, and butanediol. Claim 10 A lithium-ion metal hybrid battery comprising a composite for a lithium-ion metal hybrid battery negative electrode manufactured through a method described in any one of claims 4 to 9. Claim 11 delete Claim 12 delete

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