KR20180053481A - Manufacturing method of lithium anode containing protection layer, lithium anode manufactured thereby and lithium secondary battery applied thereby - Google Patents

Abstract

One embodiment of the present invention provides a manufacturing method of a lithium negative electrode containing a surface protection layer which comprises the following steps: applying a protective metal precursor solution to a lithium metal (step 1); and reacting the lithium metal coated with the precursor solution to form a lithium-protective metal alloy layer on the surface (step 2). According to the manufacturing method of the present invention, the stability of lithium can be increased by dendrite inhibition.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium secondary battery, and more particularly, to a lithium secondary battery having a surface protective layer formed thereon, a lithium negative electrode produced thereby, and a lithium secondary battery using the same. BACKGROUND OF THE INVENTION < RTI ID =

[0001] The present invention relates to a lithium negative electrode manufacturing method, a lithium negative electrode produced thereby, and a lithium secondary battery using the same. More particularly, the present invention relates to a lithium negative electrode comprising lithium-silicon based, lithium- Alloy system) as a surface protective layer, a lithium negative electrode produced thereby, and a lithium secondary battery using the lithium negative electrode.

In recent years, interest in the development of environmentally friendly energy production technology and energy storage devices has been increasing to cope with global warming and environmental pollution. As a result, the demand for increasing the energy density of lithium secondary batteries is also increasing. The battery system using the lithium metal as the cathode can maximize the voltage of the battery even if the conventional anode technique is used due to the lithium metal having the lowest oxidation-reduction potential, and it is possible to maximize the voltage of the battery by 10 times (3,884 mAh / g) can be expressed, thereby maximizing the energy density per mass of the battery. Also, the energy density per unit volume is as high as 2,047 mAh / cm ³ , which has the advantage of reducing the volume.

Although the lithium metal cathode technology capable of manifesting high energy density has received a lot of light, it has not been actually applied due to a lot of safety problems. Since lithium metal follows the reversible adsorption / desorption of lithium ions during charging and discharging, non-uniform adsorption may occur depending on the current distribution in the electrode, and lithium dendrite can be formed as a result. Once the dendrite is formed, the current concentrates to the dendrite, which tends to increase the dendrite formation. As a result, a short circuit occurs in the battery, resulting in thermal runaway, which can seriously affect safety such as explosion and fire of the battery I can go crazy.

In the prior art, techniques for coating various polymers onto lithium metal as physical shielding films exist. Korean Patent Laid-Open Publication No. 10-2012-0122674 discloses a current collector; A negative electrode active material layer disposed on the current collector; And an organic-inorganic hybrid protective layer disposed on the anode active material layer; And the lithium ion conductivity of the polymer contained in the composite protective layer is 10 ^-4 S / cm or less. In addition, many techniques for stabilizing lithium metal by adding an additive to an electrolyte have been studied. However, there is a lack of research on protecting lithium metal by forming a lithium-alloy-based protective layer on the surface of lithium metal.

Korean Patent Publication No. 10-2012-0122674

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a method of manufacturing a lithium- , A metal capable of forming an alloy with lithium such as potassium, zinc and nickel) to form a thin lithium alloy layer on the surface of the lithium metal to form a stable solid electrolyte interface SEI (Solid Electrolyte Interface) layer between the lithium alloy and the electrolyte , 2) a lithium negative electrode having a surface protective layer formed by increasing the stability of lithium through dendrite inhibition due to the lithium transfer of the alloy layer having a higher potential than that of lithium, and a lithium negative electrode produced by the method.

According to an aspect of the present invention, there is provided a method of manufacturing a lithium secondary battery including: applying a protective metal precursor solution to a lithium metal (step 1); And forming a lithium-protective metal alloy layer on the surface by reacting the lithium metal coated with the precursor solution (step 2).

In one embodiment, the protective metal precursor of step 1 is one metal selected from the group consisting of tin, silicon, germanium, aluminum, antimony, gold, silver, indium, copper, magnesium, sodium, potassium, May be used.

In one embodiment, the protective metal precursor of step 1 can be a tin precursor, which is selected from the group consisting of tin chloride (SnCl ₂ ), tin tetrachloride (SnCl ₄ ), tin acetate (Sn (CH ₃ COO) ₂ ) , And tin acetylacetonate (Sn (CH ₃ COCHCOCH ₃ ) ₂ ).

In one embodiment, the protective metal precursor of step 1 may be a silicon precursor, and the silicon precursor may be selected from the group consisting of silicon tetrachloride (SiCl ₄ ), dichlorosilane (SiH ₂ Cl ₂ ), hexachlorodisilane (Si ₂ Cl ₆ ), Silane (SiH ₄ ), tetraethoxysilane (Si (C ₂ H ₅ O) ₄ ), and silicon tetraisocyanate (Si (NCO) ₄ ).

In one embodiment, the application of the precursor solution of step 1 may be carried out so that the coating thickness is 10 nm to 50 탆, but it may be carried out within a thickness that does not increase the resistance to the entry and exit of lithium depending on the coating thickness ..

In one embodiment, the reaction temperature in the step 2 may be 25 to 200 ° C, and the reaction may be performed within a temperature range in which the lithium metal is not melted.

In one embodiment, the reaction time in step 2 may be from 0.5 minutes to 24 hours, and may be carried out within a period of time during which no side reaction with lithium metal occurs during the reaction.

In one embodiment, the lithium-protective metal alloy layer in step 2 is a lithium-tin alloy, a lithium-silicon alloy, a lithium-germanium alloy, a lithium-aluminum alloy, a lithium- antimony alloy, A lithium-iron alloy, a lithium-gold alloy, a lithium-indium alloy, a lithium-copper alloy, a lithium-magnesium alloy, a lithium-sodium alloy, a lithium-potassium alloy, And the like.

According to another aspect of the present invention, there is provided a lithium secondary battery comprising: a lithium metal; And a lithium-protective metal alloy layer formed on the lithium metal surface to a thickness of 10 nm to 50 占 퐉.

In one embodiment, the lithium-protecting metal alloy layer is formed of a lithium-tin alloy, a lithium-silicon alloy, a lithium-germanium alloy, a lithium-aluminum alloy, a lithium-antimony alloy, A lithium-iron alloy, a lithium-iron alloy, a lithium-iron alloy, a lithium-iron alloy, a lithium-indium alloy, a lithium-copper alloy, a lithium-magnesium alloy, a lithium- May include alloys of species.

In order to achieve the above object, another aspect of the present invention is a lithium secondary battery comprising: the lithium negative electrode of the ninth aspect; Electrolyte; And a positive electrode.

According to an aspect of the present invention, there is provided a lithium secondary battery comprising: a lithium-protective metal alloy layer formed on a surface of a lithium metal and applying the lithium-protective metal alloy layer as a negative electrode of a lithium secondary battery to minimize pitch generation during lithium adsorption and desorption, The charge / discharge cycle characteristics of the lithium secondary battery can be improved by suppressing the dendrite growth of the lithium negative electrode.

It should be understood that the effects of the present invention are not limited to the above effects and include all effects that can be deduced from the detailed description of the present invention or the configuration of the invention described in the claims.

FIG. 1 is a flowchart showing an example of a method of manufacturing a lithium negative electrode having a surface protective layer according to an embodiment of the present invention.
FIG. 2 is a view illustrating an example of a method of manufacturing a lithium anode having a surface protection layer according to an embodiment of the present invention. Referring to FIG.
FIG. 3 is a photograph showing a comparison between Examples 1 and 2 of the present invention and lithium metal.
4 is a view illustrating an example of a lithium coin cell including a lithium negative electrode having a surface protection layer according to an embodiment of the present invention.
5 is a graph showing charge-discharge cycle characteristics of Examples 3 and 4 and Comparative Example 1 of the present invention.
FIG. 6 is a graph showing electrochemical impedance spectroscopy performed before and after 10 cycle charging and discharging of Examples 3 and 4 and Comparative Example 1 of the present invention. FIG.
7 is a photograph of a surface of a negative electrode surface taken before and after 10 cycle charging and discharging of Comparative Example 1 of the present invention, taken through a scanning electron microscope.
8 is a photograph of a cathode surface photograph taken before and after 10 cycle charging and discharging according to Example 3 of the present invention through a scanning electron microscope.
FIG. 9 is a photograph of a cathode surface photograph taken before and after 10 cycles charging and discharging according to Example 4 of the present invention through a scanning electron microscope. FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving it will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings.

It should be understood, however, that the present invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. To fully inform the inventor of the category of invention. Further, the present invention is only defined by the scope of the claims.

Further, in the following description of the present invention, if it is determined that related arts or the like may obscure the gist of the present invention, detailed description thereof will be omitted.

According to an aspect of the present invention,

(Step 1) (S10) of applying a protective metal precursor solution to the lithium metal; And

And a step (S20) of reacting the lithium metal coated with the precursor solution to form a lithium-protective metal alloy layer on the surface (step S20).

Hereinafter, a method of manufacturing a lithium negative electrode having a surface protective layer according to one aspect of the present invention will be described in detail for each step.

In the method for manufacturing a lithium negative electrode having a surface protective layer according to one aspect of the present invention, the step 1 (S10) applies a protective metal precursor solution to lithium metal.

The protective metal in step 1 may be a metal capable of forming an alloy with lithium such as tin, silicon, germanium, aluminum, antimony, silver, gold, indium, copper, magnesium, sodium, potassium, zinc, nickel, May be tin or silicon.

The protective metal precursor of step 1 may be a tin precursor such as SnCl ₂ , SnCl ₄ , Sn (CH ₃ COO) ₂ , Sn (Sn (CH ₃ COCHCOCH ₃ ) ₂ ), and may preferably contain at least one selected from the group consisting of tin tetrachloride.

If a tin precursor is used as the protective metal precursor of step 1, a lithium-tin alloy layer may be formed in a subsequent step (step 2).

The protective metal precursor of step 1 may be a silicon precursor and the silicon precursor may be silicon tetrachloride (SiCl ₄ ), dichlorosilane (SiH ₂ Cl ₂ ), hexachlorodisilane (Si ₂ Cl ₆ ), silane (SiH ₄ ) , Tetraethoxysilane (Si (C ₂ H ₅ O) ₄ ) and silicon tetraisocyanate (Si (NCO) ₄ ), and preferably may contain silicon tetrachloride have.

If a silicon precursor is used as the protective metal precursor of step 1, a lithium-silicon alloy layer may be formed in a subsequent step (step 2).

The precursor solution of step 1 may be prepared by mixing a solution of tin tetrachloride hydrate in a solvent.

As another specific example, the precursor solution of step 1 may be prepared by mixing a solution of a silicon tetrachloride hydrate in a solvent.

The solvent may be selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), acetonitrile (ACN), acetone, dimethylformamide (DMF), N-methylpyrrolidinone ), Dimethylacetamide (DMA), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), propylene carbonate (PC), ethylene carbonate (EC) and dimethyl carbonate v: v), ethylenecarbonate (EC) and propylene carbonate (PC) polymers (the ratio varies in v: v), and dimethyl ether (DME).

The application of the precursor solution of step 1 above may be carried out by a method such as drop casting, dip coating, transfer coating and the like, preferably, through drop casting.

The application of the precursor solution of step 1 above can be carried out so that the coating thickness is 10 nm to 50 m, preferably 100 nm to 10 m, and the applied thickness does not lead to an increase in resistance . When the coating thickness is less than 10 nm, there is a possibility that the pitch of the rechargeable lithium secondary battery to be described later will be increased and the stability of the lithium secondary battery may be deteriorated. When the coating thickness exceeds 50 탆, Layer may act as a resistor, which may cause a problem of resistance increase.

The step 1 may form an alloy with a lithium metal having a high reactivity according to the following Reaction Scheme 1, and it is expected that the alloy plays a role of forming a stable solid electrolyte interface (SEI) layer and a physical protective layer of a lithium secondary battery described later.

[Reaction Scheme 1]

xLi ⁺ + xe ^- + yM? Li _x M _y (M = Si, Sn, Ge ...)

When the tin precursor is used as the protective metal precursor in the step 1, Li _x Sn _y (Li ₂₂ Sn ₅ Li ₇ Sn ₂ , Li ₁₃ Sn ₅ Li ₇ Sn ₂ , Li ₅ Sn ₂ , LiSn , Li ₂ Sn ₅ ) may be formed.

When a silicon precursor is used as the protective metal precursor in the step 1, Li _x Si _y (Li ₂₂ Si ₅ , Li ₁₃ Si ₄ , Li ₇ Si ₃ , Li ₁₂ Si ₇ and LiSi) An intermetallic compound may be formed.

Step 1 may be performed by applying a protective metal precursor and a binder onto a substrate and transferring the protective metal precursor and the binder onto a lithium metal surface, as shown in FIG. 2 (c), instead of applying the protective metal precursor solution. The substrate may be a copper foil.

In the step 1, instead of applying the protective metal precursor solution, a lithium metal electrode and a counterpart protective metal electrode are disposed on a solution mixed with a protective metal precursor and an electrolyte as shown in FIG. 2 (d) ≪ / RTI >

In step (S20), the lithium metal coated with the precursor solution is reacted to form a lithium-protective metal alloy layer on the surface, in the method for manufacturing a lithium anode having a surface protective layer according to one aspect of the present invention.

The reaction temperature of the step 2 may be 25 캜 to 200 캜, preferably 25 캜 to 100 캜. If the reaction temperature is lower than 25 ° C, the reaction may not be easily performed due to the low temperature. Therefore, the content of impurities is high, so there is a possibility that the charge / discharge characteristics of the lithium secondary battery may deteriorate. If the temperature is higher than 200 ° C, the problem of damage to the metal itself may occur due to melting of the lithium metal.

The reaction time of step 2 may be performed for 0.5 minutes to 24 hours, preferably for 1 minute to 12 hours. If the reaction time is less than 0.5 minutes, the lithium-protective metal alloy layer may not be uniformly formed. If the reaction time is more than 24 hours, a side reaction other than the formation of the lithium- There is a possibility that the characteristics of the lithium secondary battery may deteriorate when used as a cathode of the lithium secondary battery.

Through the reaction of step 2, the lithium-protecting metal alloy layer can be easily formed. The lithium-protective metal alloy layer may be formed of a lithium-tin alloy, a lithium-silicon alloy, a lithium-germanium alloy, a lithium-aluminum alloy, a lithium-antimony alloy, a lithium- A lithium-magnesium alloy, a lithium-magnesium alloy, a lithium-magnesium alloy, a lithium-sodium alloy, a lithium-potassium alloy, a lithium-zinc alloy and a lithium-nickel alloy . When the protective metal precursor of step 1 is a tin precursor, a lithium-tin alloy layer may be formed through the reaction of step 2, wherein the lithium-tin alloy layer comprises Li _x Sn _y (Li ₂₂ Sn ₅ And an intermetallic compound such as Li ₇ Sn ₂ , Li ₁₃ Sn ₅ Li ₇ Sn ₂ , Li ₅ Sn ₂ , LiSn, and Li ₂ Sn ₅ ). When the protective metal precursor of step 1 is silicon, a lithium-silicon based alloy layer may be formed through the reaction of step 2, wherein the lithium-silicon based alloy layer is Li _x Si _y (Li ₂₂ Si ₅ , Li ₁₃ Si ₄ , Li ₇ Si ₃ , Li ₁₂ Si _7, and LiSi).

The lithium negative electrode comprising the lithium-protective metal alloy layer formed through steps 1 and 2 suppresses pitch growth and dendrite growth on the surface of the negative electrode even when repeatedly charged and discharged when applied to a lithium secondary battery, and exhibits stable lifetime characteristics .

According to another aspect of the present invention,

(Steps 1 and 2, S10 and S20)

Lithium metal; And a lithium-protective metal alloy layer formed on the lithium metal surface to a thickness of 10 nm to 50 占 퐉.

The lithium-protective metal alloy layer may be formed of a lithium-tin alloy, a lithium-silicon alloy, a lithium-germanium alloy, a lithium-aluminum alloy, a lithium-antimony alloy, a lithium- A lithium-magnesium alloy, a lithium-magnesium alloy, a lithium-magnesium alloy, a lithium-sodium alloy, a lithium-potassium alloy, a lithium-zinc alloy and a lithium-nickel alloy .

Due to the lithium-protective metal alloy layer formed on the lithium metal surface to a thickness of 10 nm to 50 탆, a stable and low-resistance solid electrolyte interface (SEI) layer can be formed in the lithium secondary battery to which the lithium- Adsorption and desorption can be stably performed.

According to another aspect of the present invention,

A lithium negative electrode having a surface protective layer formed thereon; Electrolyte; And a positive electrode.

The secondary battery may further include a separation membrane disposed between the cathode and the anode.

The lithium secondary battery may be classified into a lithium ion battery, a lithium ion polymer battery, and a lithium polymer battery depending on the type of separation membrane and electrolyte to be included, and may be classified into a cylindrical shape, a square shape, a coin shape, And can be divided into a bulk type and a thin film type depending on the size, and one aspect of the present invention can include all of them.

The lithium secondary battery can be manufactured by disposing a separator between a cathode and an anode to manufacture an electrode assembly, placing the electrode assembly in a case, and injecting a non-aqueous electrolyte containing a lithium salt. The negative electrode may be a lithium negative electrode having a surface protective layer according to one aspect of the present invention.

The separator may be an insulating thin film having high ion permeability and mechanical strength.

The pore diameter of the separation membrane may be 0.01 탆 to 10 탆, and the thickness may be 5 탆 to 300 탆, but is not limited thereto.

The separator may be a sheet or nonwoven fabric made of olefin-based polymer such as polypropylene which is resistant to chemical and hydrophobic, glass fiber, polyethylene, or the like. Further, when a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as a separation membrane.

The electrolyte may comprise a non-aqueous electrolyte and a lithium salt. The non-aqueous electrolyte may be a non-aqueous electrolyte, a solid electrolyte, an inorganic solid electrolyte, or the like.

Examples of the nonaqueous electrolyte include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylenecarbonate, dimethyl carbonate, diethyl carbonate, Such as tetrahydrofuran, tetrahydrofuran (THF), 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylform Amide, dioxolan, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolan derivatives, sulfolane, methylsulfolane, 1,3-dimethyl- -Ammonic organic solvents such as imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyrophosphate and ethyl propionate can be used.

Examples of the organic solid electrolyte include a polymer electrolyte such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, an agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, Polymers containing ionic dissociation groups, and the like can be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitrides, halides and sulfates of Li such as Li ₄ SiO ₄ -LiI-LiOH and Li ₃ PO ₄ -Li ₂ S-SiS ₂ can be used.

The lithium salt is a substance which is easily dissolved in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , _{LiAsF 6, LiSbF 6, LiAlCl 4} , CH 3 SO 3 Li, CF 3 SO 3 Li, (CF 3 SO 2) can be used ₂ NLi, such as chloroborane lithium, lower aliphatic carboxylic acid lithium, lithium tetraphenyl borate.

The secondary battery is a surface protective layer of a lithium negative electrode, suppressing non-uniform detachment of lithium ions, suppressing pitch and dendritic growth, and thereby improving lifetime characteristics.

Hereinafter, the present invention will be described in more detail with reference to Examples and Experimental Examples. However, the following examples and experimental examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

≪ Example 1 > Preparation of a lithium negative electrode having a surface protective layer 1

Step 1: As shown in Fig. 3, a tin tetrachloride (SnCl4) solution was applied to lithium metal to a thickness of 30 mu m by drop casting.

Step 2: After the application, the reaction was conducted at a temperature of 25 캜 for 1 minute to prepare a lithium anode having a lithium-tin alloy layer with a thickness of 30 탆.

≪ Example 2 > Preparation of a lithium negative electrode having a surface protective layer 2

Step 1: As shown in Fig. 3, a solution of silicon tetrachloride (SiCl4) was applied to lithium metal to a thickness of 50 mu m by drop casting.

Step 2: After the application, the reaction was carried out at a temperature of 25 캜 for 3 minutes to prepare a lithium anode having a 20 탆 thick lithium-silicon alloy layer.

≪ Example 3 > Preparation of lithium coin cell 1

As shown in FIG. 4, the lithium negative electrode prepared in Example 1; And a cathode made of a lithium metal thin film. The electrodes were laminated and compressed with a polyethylene separator having a thickness of 20 mu m, and then an electrolyte was injected to prepare a coin cell. At this time, a solution obtained by dissolving LiPF6 in a concentration of 1M in a mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) (EC: DMC = 1: 1 by volume) as an electrolyte was used.

Example 4 Lithium Coin Cell Production 2

A coin cell was prepared in the same manner as in Example 3, except that the lithium negative electrode prepared in Example 2 was used as a negative electrode.

≪ Comparative Example 1 > Preparation of lithium coin cell 3

A coin cell was prepared in the same manner as in Example 3 except that a pure lithium negative electrode was used as a negative electrode.

EXPERIMENTAL EXAMPLE 1 Evaluation of charge / discharge characteristics of a lithium coin cell

The charge and discharge cycle characteristics were measured by repeatedly applying positive and negative charges to the coin cell prepared in Examples 3 and 4 and Comparative Example 1 for 1 hour under the condition of 1 mA / cm 2. The results are shown in FIG.

As shown in Fig. 5, in the case of Comparative Example 1 in which the lithium alloy layer was not present, the lifetime after 55 cycles was reached, while 170 cycles in Example 3 and 180 cycles in Example 4 were reached, Respectively.

Experimental Example 2 Electrochemical Impedance Spectroscopy Test of Lithium Coin Cell

The electrochemical impedance spectroscopy of the coin cells prepared in Examples 3 and 4 and Comparative Example 1 was performed, and the coin cells obtained by charging and discharging the prepared coin cells 10 times were also measured. The results are shown in FIG. 6 (a) And (b).

6 (a) and 6 (b) show how the surface resistance of the lithium metal changes as the adsorption and desorption of lithium in the coin cell occurs.

As shown in Fig. 6 (a), in Example 3 in which a tin-lithium based alloy layer was formed, it was confirmed that the resistance was reduced in comparison with Comparative Example 1 in which no tin-lithium based alloy layer was formed. And showed a small resistance value.

As shown in FIG. 6 (b), the results of electrochemical impedance spectroscopy after driving the coin cell for 10 cycles showed that Comparative Example 1, which was composed of a pure lithium cathode which was initially unstable in a life time characteristic of less than 10 cycles, It is observed that the resistance becomes lower than the value before 10 cycles because the electrolyte is stabilized while forming the interface (SEI) layer. However, it was also confirmed that the resistance was also higher than that of the lithium-tin alloy and the lithium-silicon alloy.

That is, in Examples 3 and 4, it was confirmed that a stable solid electrolyte interface (SEI) layer was formed on the protective film and that the protective film lowered the resistance of the metal surface.

<Experimental Example 3> Surface analysis of a coin cell cathode

The coin cell and the coin cell fabricated in Examples 3 and 4 and Comparative Example 1 were photographed through a scanning electron microscope (SEM) on the surface of the coin cell in which the 10 cycle charging / discharging test was performed through Experimental Example 1 , And the results are shown in Figs.

As shown in FIGS. 7 to 9, the surface of the negative electrode in the state where lithium was finally desorbed after progress of adsorption and desorption of lithium maintained a uniform shape in all of Examples 3 and 4 and Comparative Example 1 before charge / discharge test, It was confirmed that the negative electrode of Comparative Example 1 after the cycle charge / discharge had a large pitch (groove) due to the non-uniform desorption of lithium.

This pitch induces a non-uniform current distribution in the subsequent charge / discharge cycle and ultimately induces dendrite growth of the lithium metal.

On the other hand, in Examples 3 and 4 in which a lithium-tin alloy and a lithium-silicon based alloy layer were formed, the shape of the surface of the negative electrode was different from each other, but Example 3 found a form in which lithium was covered in a relatively uniform and rounded shape And it can be seen that the fourth embodiment maintains a uniform and flat shape well.

It was confirmed that the lithium alloy protective layer formed in Examples 3 and 4 acted as a physical protective layer in the adsorption and desorption of lithium metal, and the stable and low-resistance solid electrolyte interface (SEI) layer as a result of electrochemical impedance spectroscopy So that the adsorption and desorption of lithium can be stably performed.

These results show that the lifetime characteristics and stability of the lithium anode can be increased.

Although the present invention has been described with respect to a method for producing a lithium negative electrode having a surface protective layer according to one aspect of the present invention, a lithium negative electrode manufactured thereby, and a lithium secondary battery using the same, It is apparent that various modifications can be made.

Therefore, the scope of the present invention should not be construed as being limited to the embodiments described, but should be determined by equivalents to the appended claims, as well as the following claims.

It is to be understood that the foregoing embodiments are illustrative and not restrictive in all respects and that the scope of the present invention is indicated by the appended claims rather than the foregoing description, It is intended that all changes and modifications derived from the equivalent concept be included within the scope of the present invention.

Claims (11)

Applying a protective metal precursor solution to the lithium metal (step 1); And
And a step of forming a lithium-protective metal alloy layer on the surface by reacting the lithium metal coated with the precursor solution (step 2).
The method according to claim 1,
The protective metal precursor of step &lt; RTI ID = 0.0 &gt; 1 &
Wherein the surface protective layer is a precursor including a metal selected from the group consisting of tin, silicon, germanium, aluminum, antimony, gold, silver, indium, copper, magnesium, sodium, potassium, A method for manufacturing a lithium negative electrode.
The method according to claim 1,
Wherein the protective metal precursor of step 1 is a tin precursor,
The tin precursor is tin chloride (SnCl _2), tin tetrachloride (SnCl _4), acetate, tin _{(Sn (CH 3 COO) 2} ), tin acetylacetonate _{(Sn (CH 3 COCHCOCH 3)} 2) selected from the group consisting of 1 Wherein the surface protective layer is formed on the surface of the anode.
The method according to claim 1,
Wherein the protective metal precursor of step 1 is a silicon precursor,
The silicon precursor may be selected from the group consisting of silicon tetrachloride (SiCl ₄ ), dichlorosilane (SiH ₂ Cl ₂ ), hexachlorodisilane (Si ₂ Cl ₆ ), silane (SiH ₄ ), tetraethoxysilane (Si (C ₂ H ₅ O) ₄ ) and silicon tetraisocyanate (Si (NCO) ₄ ). 2. The method of manufacturing a lithium negative electrode according to claim 1,
The method according to claim 1,
The application of the precursor solution of step 1 above,
And the coating thickness is 10 nm to 50 占 퐉.
The method according to claim 1,
The reaction temperature of step 2 is:
Lt; RTI ID = 0.0 &gt; 25 C &lt; / RTI &gt; to &lt; RTI ID = 0.0 &gt; 200 C. &lt; / RTI &gt;
The method according to claim 1,
The reaction time of step 2 is,
Wherein the surface protective layer is formed on the surface of the anode.
The method according to claim 1,
The lithium-protecting metal alloy layer of step 2 is a lithium-
A lithium-iron alloy, a lithium-iron alloy, a lithium-iron alloy, a lithium-iron alloy, a lithium-tin alloy, a lithium-silicon alloy, a lithium-germanium alloy, a lithium-aluminum alloy, , A lithium-magnesium alloy, a lithium-sodium alloy, a lithium-potassium alloy, a lithium-zinc alloy, and a lithium-nickel alloy. Wherein the lithium negative electrode is formed.
5. A process for the preparation of a compound according to claim 1,
Lithium metal; And a lithium-protective metal alloy layer formed on the lithium metal surface to a thickness of 10 nm to 50 占 퐉.
10. The method of claim 9,
The lithium-
A lithium-iron alloy, a lithium-iron alloy, a lithium-iron alloy, a lithium-iron alloy, a lithium-tin alloy, a lithium-silicon alloy, a lithium-germanium alloy, a lithium-aluminum alloy, , A lithium-magnesium alloy, a lithium-sodium alloy, a lithium-potassium alloy, a lithium-zinc alloy, and a lithium-nickel alloy. Formed lithium cathode.
A lithium negative electrode according to claim 9; Electrolyte; And a positive electrode.

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