KR102198785B1 - Anode Material for Lithium Secondary Battery Comprising Tin-Fullerene Complex and Preparation Method Thereof - Google Patents

Abstract

The present invention relates to a negative electrode active material for a lithium secondary battery including a tin-fullerene composite (Sn-PC ₆₀ ; SPC), a negative electrode for a lithium secondary battery including the same, a lithium secondary battery, and a method of manufacturing the same.
In the tin-fullerene composite (Sn-PC ₆₀ ; SPC) of the present invention, nano-sized tin particles are uniformly distributed to prevent electrode degradation according to cycles (self-releasing effect on electrode volume expansion), and tin-tin oxide- By forming a layered structure of plasma polymerization fullerene, the rate characteristics are improved (the effect of accelerating the diffusion rate of lithium ions).

Description

Anode Material for Lithium Secondary Battery Comprising Tin-Fullerene Complex and Preparation Method Thereof}

The present invention relates to a negative electrode active material for a lithium secondary battery including a tin-fullerene composite (Sn-PC ₆₀ ; SPC), a negative electrode for a lithium secondary battery including the same, a lithium secondary battery, and a method of manufacturing the same.

Lithium ion batteries are widely used in cell phones, laptops, and digital cameras because of their high density, light weight, and advantage in making high-capacity batteries. Recently, performance improvement of lithium-ion batteries is also required due to electric devices that require high capacity, long life, and excellent efficiency characteristics.

To replace the existing graphite material with a theoretical capacity of 372 mAh·g ^-1 , use a metal-based anode material, silicon material (Si), or tin (Sn) that exhibits a theoretical capacity three times higher than graphite. The research using the is continued steadily. However, the tin electrode material also has a problem in that an alloy reaction with lithium (Li ₂₂ Sn ₅ ) occurs during charging and discharging, resulting in volume expansion of the electrode (about 259% compared to the previous one). The volume expansion of the electrode causes structural instability due to cracking of the tin particles, and the performance gradually deteriorates due to the unstable interfacial characteristics of the electrochemical environment, which has limitations in achieving high capacity and high output long life characteristics.

Accordingly, in order to improve the problem of the tin electrode, a tin-carbon composite electrode having a York-shell structure (Small., Vol. 11, 2157-2163, 2015), in which tin nanoparticles were included in a porous carbon support containing a large amount of nitrogen. Tin electrode (Nano Energy., Vol. 19, 486-494, 2016), a carbon-carbon nanotube type tin electrode containing Ni-Sn-P of double metal porosity (Small, Vol. 13, 1700521, 2017) ), etc., in which tin particles are encapsulated in a porous carbon support, or other metal materials are used to prepare a tin-based composite.

In order to prepare such a complex, a method of reacting by heating in a liquid phase is mainly used. When the electrode active material is synthesized in this way, a uniform complex is formed due to the interaction between various nano-sized particles including tin. There is a problem that it is difficult to manufacture.

Under this background, the inventors of the present invention have conducted intensive research efforts to develop a tin-based composite that can effectively mitigate the volume expansion of tin and uniformly distribute nano-sized tin particles, as a result of the tin-fullerene composite (Sn-PC ₆₀ ; In the case of SPC), nano-sized tin particles are evenly distributed to prevent electrode deterioration according to cycles (self-relief effect on electrode volume expansion), and a hierarchical structure of tin-tin oxide-plasma polymerization fullerene is formed. It was confirmed that the characteristics were improved (the effect of accelerating the diffusion rate of lithium ions), and the present invention was completed.

One object of the present invention is to provide a method for manufacturing a negative electrode active material for a lithium secondary battery comprising the step of polymerizing a tin precursor gas and fullerene using RF plasma.

Another object of the present invention is a lithium secondary comprising a tin (Sn) core-tin oxide (SnO ₂ ) core-shell-plasma polymerized fullerene (PC ₆₀ ) matrix structure of a tin-fullerene complex (Sn-PC ₆₀ ; SPC). It is to provide an anode active material for batteries.

Another object of the present invention is to provide a negative electrode for a lithium secondary battery comprising a tin-fullerene composite (Sn-PC ₆₀ ; SPC).

Another object of the present invention is to provide a lithium secondary battery including a tin-fullerene composite (Sn-PC ₆₀ ; SPC).

In order to achieve the above object, one aspect of the present invention provides a method of manufacturing a negative electrode active material for a lithium secondary battery comprising the step of polymerizing a tin precursor gas and fullerene using RF plasma.

The term "tin precursor gas" in the present invention are tin-fullerene complex _{(Sn-PC 60; SPC)} -; the fullerene conjugate (SPC Sn-PC ₆₀₎ means a precursor material of tin and tin used to prepare the As long as it can be manufactured, there is no limit to its kind. Specifically, an organic compound containing tin may be used, and more specifically, tetrakis-dimethylaminotin (Sn[N(CH ₃ ) ₂ ] ₄ ) or tetramethyltin (Sn(CH ₃ ) ₄ ) may be used. However, it is not limited thereto.

The term "fullerene" of the present invention refers to a carbon cluster C ₆₀ formed by combining 60 carbon elements in the shape of a soccer ball, which forms a'nano soccer ball' having a diameter of about 1 nm.

The term "lithium secondary battery" of the present invention refers to a secondary chemical battery that can repeat a reversible reaction that converts chemical energy into electrical energy in the discharging process and vice versa in the charging process. It is a kind of battery. Lithium ions present in an ionic state move from the positive electrode to the negative electrode during charging and from the negative electrode to the positive electrode during discharge, and are also called lithium ion batteries. The lithium secondary battery has high voltage and excellent energy density characteristics due to a potential difference between two electrodes. In general, it is composed of a positive electrode active material, a negative electrode active material, a separator, and an electrolyte, and in order to operate smoothly, structural stability in two electrodes in which lithium ions are inserted and desorbed during charging and discharging is very important.

The term "anode material" of the present invention is a material that accepts lithium ions from a negative electrode during charging, and is also called a negative electrode material. Materials with a low reduction potential are mainly used, and during discharge, the oxidation reaction of stored lithium atoms occurs, and electrons generated in the oxidation reaction move to the anode along the lead to generate electrical energy. In the charging and discharging process, there should be little structural change, and the speed of electron transfer and lithium ion diffusion should be fast.

In the present invention, the polymerization may be performed through thermal evaporation chemical vapor deposition using RF plasma.

The term of the present invention, "radio frequency plasma assisted thermal evaporation chemical vapor deposition (RF-PATE CVD)" is also called thermal evaporation chemical vapor deposition using RF plasma. It refers to a method of forming a thin film by applying plasma to excitation at a high energy level to cause a spontaneous chemical reaction to deposit a reaction product on a substrate. The term'plasma' refers to a gaseous state separated by negatively charged electrons and positively charged ions at ultra-high temperature. In the case of chemical vapor deposition using plasma, the reaction occurs thermally and the gaseous raw material is discharged. It is chemically activated and has a large reactivity, so that the process can be performed at low temperatures.

In a specific embodiment of the present invention, tetramethyltin (Sn(CH ₃ ) ₄ ) gas and fullerene (C ₆₀ ) powder were polymerized using RF plasma. At this time, the basic atmospheric pressure inside the chamber was maintained below 1.0x10 ^-5 Torr, and then the copper foil to be used as a current collector was heated to 250°C, and then, 30 sccm of argon gas was introduced into the chamber to reduce the process pressure to 42 mTorr. Adjusted. A radio frequency of 300W was introduced to generate RF plasma, and argon gas, a carrier gas, introduced gaseous tedramethyltin (Sn(CH ₃ ) ₄ ) gas into the chamber at a flow rate of 10 sccm. At the same time, the tungsten boat was heated by a direct current power source to evaporate the fullerene (C ₆₀ ) powder, and a tin-fullerene composite (Sn-PC ₆₀ ; SPC) was deposited on the cleanly cleaned surface of the 15 μm-thick copper foil.

At this time, the polymerization may be carried out at an internal atmospheric pressure of 1.0x10 ^-5 Torr or less, specifically 1.0x10 ^-9 to 1.0x10 ^-5 Torr, 1.0x10 ^-8 to 1.0x10 ^-5 Torr, 1.0x10 ^-7 to 1.0 It may be performed at x10 ^-5 Torr, 1.0x10 ^-6 to 1.0x10 ^-5 Torr, but is not limited thereto.

In this case, the polymerization may be performed at a current collector temperature of 200 to 300°C, specifically 200 to 300°C, 220 to 280°C, 240 to 260°C, more specifically 250°C, but limited thereto. It does not become.

At this time, the polymerization may be performed at a carrier gas: tin precursor gas flow ratio of 8:1 to 1:3, specifically 8:1 to 1:3, 5:1 to 1:1, 4:1 to 2: 1, more specifically, it may be performed at a 3:1 carrier gas:tin precursor gas flow ratio, but is not limited thereto.

At this time, the polymerization may be carried out at a radio frequency of 250 to 350 W, specifically 250 to 350 W, 270 to 330 W, 280 to 320 W, 290 to 310 W, 295 to 305 W, more specifically 300 W It may be performed at the radio frequency of, but is not limited thereto.

At this time, the polymerization may be carried out at a process pressure of 30 to 50 mTorr, specifically 30 to 50 mTorr, 35 to 45 mTorr, 37 to 43 mTorr, 39 to 41 mTorr, more specifically 40 mTorr. It may be, but is not limited thereto.

Another aspect of the present invention is a lithium secondary comprising a tin (Sn) core-tin oxide (SnO ₂ ) core-shell-plasma polymerized fullerene (PC ₆₀ ) matrix structure of a tin-fullerene complex (Sn-PC ₆₀ ; SPC). Provides an anode active material for batteries.

In this case, the description of the "lithium secondary battery", the "negative electrode active material" and "fullerene" is as described above.

The anode active material for a lithium secondary battery of the present invention includes a tin (Sn) core-tin oxide (SnO ₂ ) core-shell-plasma polymerized fullerene (PC ₆₀ ) matrix structure of a tin-fullerene composite (Sn-PC ₆₀ ; SPC).

The tin-fullerene composite (Sn-PC ₆₀ ; SPC) of the present invention has a hierarchical structure composed of a tin (Sn) core-tin oxide (SnO ₂ ) core-shell-plasma polymerized fullerene (PC ₆₀ ) matrix. The initial state is a metal/n-type semiconductor/p-type semiconductor structure. The combination of these three components creates a Fermi energy level. The tin/tin oxide (Sn/SnO ₂ ) interface has an ohmic contact, and the interface between the tin oxide/plasma polymerization fullerene (SnO ₂ /PC ₆₀ ) forms a pn semiconductor junction interface. Therefore, in the charged state, an external voltage reduces the depletion zone (W) of the pn junction. The external voltage field formed at the SnO ₂ /PC ₆₀ interface allows lithium ions to move from the PC ₆₀ matrix to the tin particles through electrostatic interaction. At the same time, most free carriers in amorphous SnO ₂ attract lithium ions from the PC ₆₀ matrix to tin particles by electrostatic action. Therefore, lithium ions easily pass through the junction. A negative electrode active material containing such a tin-fullerene composite (Sn-PC ₆₀ ; SPC) is converted into a composite such as Li _x Sn and Li _y C when fully reacted with lithium, and the thin SnO ₂ existing between Sn and PC ₆₀ The interface is changed to Li _x Sn or Li ₂ O.

Li_xSn (0≤ x ≤4.4) (1)Sn ⁺ xLi + + xe ^-

Li _x Sn (0≤ x ≤4.4) (1)

Li_x0_yC (y는 임의의 값) (2)C ⁺ yLi + + ye ^-

Li _x 0 _y C (y is an arbitrary value) (2)

Sn + 2Li₂O (0≤ x ≤4.4) (3)SnO ₂ ⁺ 4Li + + 4e ^-

Sn + 2Li ₂ O (0≤ x ≤4.4) (3)

Since there are more lithium ions inside the Li _x Sn particles than the Li _y C matrix, the Li _x Sn work function is much lower than that of Li _y C and lower than that of the amorphous SnO ₂ layer. As a result, most of the free carriers in PC ₆₀ move from positive charges to negative charges. In addition, most of the free carriers in the amorphous SnO ₂ have already been changed to Li _x Sn and Li ₂ O, so they move from negative to positive charges.

On the other hand, when the electric field formation is reversed, that is, in the discharging process, the Fermi energy level of PC ₆₀ is improved, and the lithium alloyed SnO ₂ (i.e., Li _x Sn and Li ₂ O) has quite a lot of lithium ions. The Fermi energy level is lowered. And the formed electric field flows in the opposite direction. Therefore, lithium ions in Sn move easily and easily through the interface. The two interfaces formed through this mechanism, Sn/SnO ₂ and SnO ₂ /PC ₆₀ interfaces, accelerate the movement of lithium ions during the charging and discharging process, enabling rapid charging.

In a specific embodiment of the present invention, as a result of comparing the rate characteristics in half-cells of Pristine PC ₆₀ , Pristine Sn and SPC-50 electrodes, at a current density of 100 mA·g ^-1 , each of 904.35 mA·g ^-1 , Capacities of 990.93 mA·g ^-1 and 1054.11 mAh·g ^-1 at a current density of 10000 mA·g ^-1 of 211.96 mA·g ^-1 , 52.27 mA·g ^-1 and 544.33 mAh·g ^-1 respectively By indicating the capacity, it was confirmed that the rate characteristics of SPC-50 were excellent (FIG. 10). It can be seen that this is a result that the diffusion rate of lithium ions is improved by the ohmic/built-in electric field (BEF) effect as the pn junction structure is induced from the junction of the SnO ₂ /PC ₆₀ interface.

The negative active material for a lithium secondary battery of the present invention may be prepared by the above manufacturing method.

There is no limit to the weight ratio of tin (Sn) and plasma polymerization fullerene (PC ₆₀ ) of the tin-fullerene composite (Sn-PC ₆₀ ; SPC) of the present invention. Specifically, it may have a weight ratio of 85:15 to 15:85, a weight ratio of 70:30 to 30:70, a weight ratio of 60:40 to 40:60, a weight ratio of 55:45 to 45:55, or a weight ratio of 50:50, but is limited thereto. It does not become.

In a specific embodiment of the present invention, SPC-18 (Sn:PC ₆₀ =18:82 weight ratio), SPC-41 (Sn:PC ₆₀ =41:59 weight ratio), SPC-50 (Sn:PC ₆₀ =50: 50 weight ratio), SPC-59 (Sn:PC ₆₀ =59:41 weight ratio), and SPC-80 (Sn:PC ₆₀ =80:20 weight ratio) were prepared (Example 1).

The tin-fullerene composite (Sn-PC ₆₀ ; SPC) of the present invention is characterized in that nano-sized tin particles are uniformly distributed to have excellent elasticity, thereby effectively dispersing stress generated from repetitive volume expansion and contraction. This characteristic shows an effect of reducing electrode deterioration.

In the specific embodiment of the invention, Pristine PC _60, Pristine Sn, and SPC-50 Comparison of the cycle performance of the half-cell electrode, Pristine PC _60, Pristine Sn, and SPC-50 electrode in the early each 557.89, The discharge capacity was 832.00 and 858.46 mAh·g-1, but after 150 cycles, the Pristine Sn electrode showed 7.71% capacity retention and 87.52% Coulomb efficiency, while the SPC-50 electrode showed 97.35% capacity retention even after 350 cycles. And 99.54% Koolyong efficiency, it was confirmed that the cycle performance of the SPC-50 is excellent (Fig. 11).

Another aspect of the present invention provides a negative electrode for a lithium secondary battery including the negative electrode active material for a lithium secondary battery.

In this case, the description of the "lithium secondary battery", the "negative electrode active material" and "fullerene" is as described above.

In the present invention, the term "anode" generally refers to an electrode including a material that is oxidized when discharged, having an electrode level of a negative value in an electrochemical series. In particular, in a lithium secondary battery, lithium ions are inserted and stored during charging, and lithium ions are extracted and released during discharge.

The negative electrode for a lithium secondary battery of the present invention includes a tin (Sn) core-tin oxide (SnO ₂ ) core-shell-plasma polymerized fullerene (PC ₆₀ ) matrix structure of a tin-fullerene composite (Sn-PC ₆₀ ; SPC). It includes a negative electrode active material for batteries.

Another aspect of the present invention provides a lithium secondary battery including the negative active material for a lithium secondary battery.

In this case, the description of the "lithium secondary battery", the "negative electrode active material" and "fullerene" is as described above.

The lithium secondary battery of the present invention is for a lithium secondary battery including a tin (Sn) core-tin oxide (SnO ₂ ) core-shell-plasma polymerized fullerene (PC ₆₀ ) matrix structure of a tin-fullerene composite (Sn-PC ₆₀ ; SPC) Contains negative electrode active material.

In the tin-fullerene composite (Sn-PC ₆₀ ; SPC) of the present invention, nano-sized tin particles are uniformly dispersed in the plasma polymerization fullerene (PC ₆₀ ) having excellent elasticity, so that the tin particles repeatedly expand in volume during charging and discharging. And the effect of dispersing the stress generated from shrinkage to prevent electrode deterioration according to the cycle of tin particles (self-releasing effect on electrode volume expansion), and tin oxide (a-SnO ₂₎ between nano-sized tin and plasma polymerization fullerene matrix. ) As a hierarchical structure including an intermediate layer is formed, the bonding of tin oxide and plasma polymerized fullerene (PC ₆₀ ) induces a pn junction semiconductor structure, resulting in a minimum ohmic resistance and acceleration of the interfacial diffusion rate of lithium ions in the formed electric field. As a result, the rate characteristics of the electrode are improved (the effect of accelerating the diffusion rate of lithium ions).

1 shows the structure of the tin-fullerene complex (Sn-PC ₆₀ ), the self-relaxation characteristics, and the energy diagram, in which the diffusion rate of lithium ions is accelerated by the ohmic/built-in electric field (BEF) effect at the interface within the electrode. It is a schematic diagram showing the phenomenon. At this time, PC ₆₀ is a plasma polymerized fullerene (Plasma polymerized C ₆₀ ), Φ is a work function, E _BI is a built-in electric field, E _Vac is a vacuum energy level (Vacuum energy level). ), EF is the Fermi energy level, Eg is the band gap energy, CBM is the conduction-band minimum, and VBM is the maximum valence-band maximum. , W denotes a space charge region or a space depletion region.
2 is a schematic diagram of a method of manufacturing a tin-fullerene composite (Sn-PC ₆₀ ) using a thermal evaporation chemical vapor deposition method (RF-PATE CVD) using RF plasma. (A) shows the thermal evaporation chemical vapor deposition equipment including the RF source, and (B) shows the deposition process of the tin-fullerene composite (Sn-PC ₆₀ ) in the chamber.
3 is a scanning electron microscope (SEM) image of the pristine PC60 surface (a) and cross-section (d), the pristine Sn surface (b) and cross-section (e), and the SPC-50 surface (c) and cross-section (f).
4 is a graph comparing depth profiles for Pristine PC ₆₀ , Pristine Sn, and SPC-50 using X-ray photoelectron spectroscopy.
5 is a transmission electron microscope (TEM) image of the SPC-50 surface ((a) to (c)) and cross-sections ((d) to (f)).
6 is a graph comparing the components of the tin atom contained in Pristine Sn and SPC-50, analyzed using X-ray photoelectron spectroscopy.
7 is a schematic diagram of a manufacturing mechanism of a tin-fullerene composite (Sn-PC ₆₀ ) using a thermal evaporation chemical vapor deposition method (RF-PATE CVD) using RF plasma.
8 is a schematic diagram of a coin-shaped half-cell component and driving of a half-cell during charging and discharging.
9 is a graph comparing rate characteristics of Pristine Sn, SPC-80, SPC-59, SPC-50, SPC-41, SPC-18, and Pristine PC ₆₀ electrodes.
10 is a graph comparing rate characteristics in half cells of Pristine PC ₆₀ , Pristine Sn, and SPC-50 electrodes.
11 is a graph comparing cycle performance in half cells of Pristine PC ₆₀ , Pristine Sn, and SPC-50 electrodes.
12 is a graph comparing cycle performance in a complete battery using a lithium cobalt oxide (LiCoO ₂ ) positive electrode and a pristine Sn and SPC-50 negative electrode. (A) shows the cycle performance of a lithium cobalt oxide (LiCoO ₂₎ complete cell using the positive electrode and SPC-50 cathode, (B) is in the lithium cobalt oxide (LiCoO ₂₎ complete cell using the positive electrode and Pristine Sn cathode It represents the cycle performance.

Hereinafter, the present invention will be described in more detail by the following examples. However, the following examples are for illustrative purposes only, and the scope of the present invention is not limited thereto.

Example 1. Tin-fullerene complex (Sn-PC ₆₀ ; SPC)

Tetramethyltin (Sn(CH ₃ ) ₄ ) gas and fullerene (C ₆₀ ) powder were used as precursors of the tin-fullerene complex, respectively. Specifically, a tungsten boat containing a certain amount of fullerene (C ₆₀ ) powder was placed in a thermal evaporation (RF-PATE) chamber using RF plasma, and connected to a DC power source to heat the fullerene (C ₆₀ ) powder (FIG. 2) ). Before deposition, the basic atmospheric pressure inside the chamber was maintained to 1.0x10 ^-5 Torr or less, and then the copper foil to be used as a current collector was heated to 250°C. Thereafter, argon gas of 30 sccm was introduced into the chamber to adjust the process pressure to 42 mTorr, and as a radio-frequency (RF) of 300 W intensity was introduced into the reactor, RF plasma was generated. Argon gas, a carrier gas, introduced gaseous tedramethyltin (Sn(CH ₃ ) ₄ ) gas into the chamber at a flow rate of 10 sccm, and at the same time, the tungsten boat was heated by a direct current power source to produce fullerene (C ₆₀ ) powder. A tin-fullerene composite (Sn-PC ₆₀ ; SPC) was deposited on the surface of a 15 μm-thick copper foil cleaned while evaporating. In addition, the same results can be obtained by using an organic compound containing tin as a precursor instead of tetramethyltin used in the present invention.

As a result, as shown in Table 1, tin-fullerene composite tin (Sn) and plasma polymerization fullerene (PC ₆₀ ) were deposited on the surface of the copper foil at various weight ratios, respectively, according to the weight ratio of tin and plasma polymerization fullerene, SPC-18 (Sn:PC ₆₀ =18:82), SPC-41(Sn:PC ₆₀ =41:59), SPC-50(Sn:PC ₆₀ =50:50), SPC-59(Sn:PC ₆₀ =59: 41), referred to as SPC-80 (Sn:PC ₆₀ =80:20).

number Substance name Substance composition ratio One Pristine Sn Only pure tin (Sn) is deposited 2 SPC-80 80wt% of tin (Sn) and 20wt% of plasma polymerization fullerene (PC ₆₀ ) 3 SPC-59 59wt% of tin (Sn) and 41wt% of plasma polymerization fullerene (PC ₆₀ ) 4 SPC-50 50wt% of tin (Sn) and 50wt% of plasma polymerization fullerene (PC ₆₀ ) 5 SPC-41 41wt% of tin (Sn) and 59wt% of plasma polymerization fullerene (PC ₆₀ ) 6 SPC-18 18wt% of tin (Sn) and 82wt% of plasma polymerization fullerene (PC ₆₀ ) 7 Pristine PC ₆₀ Only pure plasma polymerization fullerene (PC ₆₀ ) is deposited

In addition, a tin metal thin film (Pristine Sn) in which only pure tin was deposited and a plasma-polymerized fullerene thin film (Pristine PC ₆₀ ) in which only pure plasma polymerization fullerene (PC ₆₀ ) was deposited were prepared under the same experimental conditions.

Example 2. Tin-fullerene complex (Sn-PC ₆₀ ) Structure analysis

Example 2-1. Tin-fullerene complex (Sn-PC ₆₀ ), pure tin metal thin film (Pristine Sn) and plasma polymerization fullerene thin film (Pristine PC ₆₀ ) Structure comparison analysis

For SPC-50, Pristine Sn, and Pristine PC ₆₀ prepared in Example 1, each particle size and shape were observed using a scanning electron microscope.

As a result, as shown in FIG. 3, the particle sizes of Pristine PC ₆₀ and SPC-50 were 5 nm or less and 10 nm or less, respectively, which was much smaller than Pristine Sn having a particle size of 150-200 nm. In addition, it was found that the thickness of all the electrodes was constant at about 220 nm.

In addition, for SPC-50, Pristine Sn, and Pristine PC ₆₀ prepared in Example 1, each element was analyzed using X-ray photoelectron spectroscopy.

As a result, as shown in FIG. 4, it was found that the depth profile coincided with the thickness of the electrode checked through the scanning electron microscope.

Example 2-2. Tin-fullerene complex (Sn-PC ₆₀ ) Structure detailed analysis

For the SPC-50 prepared in Example 1, a more detailed structure and arrangement of elements were analyzed using a transmission electron microscope.

As a result, as shown in FIG. 5, it was found that tin particles having a size of 10 nm or less were evenly dispersed in the PC ₆₀ matrix.

In addition, using X-ray photoelectron spectroscopy, it was found that the tin particles were surrounded by an amorphous tin oxide film on the surface, and in FIG. 6, tin oxide was an element corresponding to the binding energy of 486.4 eV and 494.9 eV.

In addition, as shown in FIG. 7, SPC-50 was found to be formed in a hierarchical structure of three other components, namely, tin (Sn)-tin oxide (SnO ₂ )-plasma polymerization fullerene (PC ₆₀ ) matrix. Tedramethyltin (Sn(CH ₃ ) ₄ ) was decomposed by argon plasma to form tin particles (Sn) and Sn (Sn) having radicals, and ionized Sn (Sn ⁴⁺ ). Afterwards, it was deposited on copper foil. After the tin particles were deposited first, Sn was deposited on the surface, and Sn ⁴⁺ was deposited on the outside. As the surface of the deposited tin particles has a positive charge, a van der Waals force (repulsive force) is generated between the deposited tin particles to maintain a certain distance. At the same time, argon plasma broke the CC bond and C=C bond of fullerene (C ₆₀ ), and formed Cy-Ox bond and Cy=Ox bond. Cy-Ox bonds and Cy=Ox bonds were reduced by oxygen atoms with high electronegativity and then reacted with Sn ^{4+ on the} surface of the tin particles to eventually form tin oxide (a-SnO ₂ ). At this time, the tin oxide was formed to a thickness of about 5 nm.

Example 3. Tin-fullerene complex (Sn-PC ₆₀ ) Preparation of a lithium ion battery containing

All electrochemical measurements were performed using a coin-type lithium ion battery (CR2032). All coin cells were manufactured in dry rooms with dew point and temperature of -100.2°C and 20°C, respectively. The separator was made of polypropylene, and the electrolyte was ethylene carbonate (C ₃ H ₄ O ₃ ): dimethyl carbonate (C ₃ H ₆ O ₃ ): ethyl methyl carbonate , C ₄ H ₈ O ₃ ) A solution in which 1 mol of lithium hexafluorophosphate (LiPF ₆ ) was mixed as a lithium salt in a solution in a volume ratio of 1:1:1 was used.

A schematic diagram of manufacturing a half-cell and driving the half-cell is shown in FIG. 8. The lithium cobalt oxide (LiCoO ₂ , LCO) positive electrode used in the manufacture of a complete battery is LCO powder, denka black as a conductive agent, and N-methyl-2-pyrrolidone (polyvinylidene fluoride) containing polyvinylidene fluoride as a binder. N-methyl-2-pyrrolidone, NMP) solution was mixed and cast in a ratio of 90% by weight, 5% by weight, and 5% by weight, respectively. The N/P ratio between the cathode and the anode was designed to be 1.1.

Example 4. Measurement of electrochemical performance

Example 4-1. Rate characteristics

The rate characteristic experiment of the battery was conducted using a marker system of Series 4000, and the experimental conditions were 100, 300, 500, 700, 1000, 2000, 3000, 5000, 10000 mA·g ^- in the cutoff voltage range of 0.01-3.00 V. A current density of ¹ was applied.

As a result of a rate characteristic experiment for optimizing the amount of fullerene polymerized with tin, as shown in FIG. 9, the highest in SPC-50 in which the ratio of tin and polymerized fullerene is 1:1 (% by weight) under the current density conditions specified above. It was confirmed that the discharge capacity was expressed, and SPC-50 was set as the final electrode condition.

As a result of comparing the rate characteristics in half-cells of Pristine PC ₆₀ , Pristine Sn and SPC-50 electrodes, as shown in FIG. 10, at current densities of 100 mA·g ⁻¹ , respectively, 904.35, 990.93, and 1054.11 mAh·g ^{− It} represents the dose of ¹ . In this regard, it was found that the SPC-50 electrode exhibited a higher capacity than the other electrodes because tin oxide (a-SnO ₂ ) surrounding the tin particle surface also contributed to the capacity expression. In addition, at a current density of 10000 mA·g ^-1 , the capacities of 211.96, 52.27, and 544.33 mAh·g ^-1 were shown, respectively. This is because the pn junction structure was induced from the junction of tin oxide and PC ₆₀ , resulting in ohmic/built-in electric It can be seen that this is a result of the improvement of the diffusion rate of lithium ions by the field (BEF) effect.

Example 4-2. Cycle performance

* The constant current experiment for cycle performance was conducted under the same conditions for the rest at a current density of 1000 mA·g-1.

Pristine PC _60, Pristine Sn, and a result of comparing the cycle performance of the SPC-50 electrode half cell of, Pristine PC _60, Pristine Sn, and SPC-50 electrodes as shown in Figure 11 is 557.89 at the beginning of each, 832.00, It showed a discharge capacity of 858.46 mAh·g-1. After 150 cycles, the pristine Sn electrode showed 7.71% capacity retention and 87.52% Coulomb efficiency, while the SPC-50 electrode showed 97.35% capacity retention and 99.54% Coulomb efficiency even after 350 cycles. It can be seen that the excellent cycle performance of SPC-50 is due to the self-relaxation characteristics of the electrode.

As a result of comparing the cycle performance in a complete battery using a lithium cobalt oxide (LiCoO ₂ ) positive electrode and a pristine Sn and SPC-50 negative electrode, as shown in FIG. 12, a pristine Sn negative electrode was formed at a current density of 1000 mA·g ^-1 . The used complete battery showed a capacity of 0.62 mAh·g ^-1 and 0.001 mAh·cm ^-2 after 150 cycles and a capacity retention rate of 0.12%, whereas the complete battery using the SPC-50 negative electrode showed 801.04 mAh·g ^-1 after 350 cycles. , It exhibited a capacity of 1.57 mAh·cm ^-2 and exhibited an excellent cycle performance of 95.27%.

Example 5. Comparison of rate characteristics and cycle performance of tin-based anode active materials according to various synthesis methods

By comparing the rate characteristics and cycle performance of the anode active material of the present invention synthesized using the thermal evaporation chemical vapor deposition method (RF-PATE CVD) using RF plasma and the tin-based anode active material synthesized using various other methods as follows. It is shown in Tables 2 and 3.

Evaporation method Anode active material Cycle performance Current density
(mA g ^-One ) Number of cycles Last cycle Reversible capacity
(mA g ^-One ) Capacity retention rate (%) Thermal evaporation using RF plasma
Chemical vapor deposition (RF-PATE CVD) Sn-PC ₆₀ 1000 5000 836.53 97.18 Microwave solvent thermal synthesis method Ball-cactus-like Ni-Sn-P@C-CNT 1000 800 504.00 63.26 Settling & heat treatment method Sn@C nanoboxes 200 500 810.00 90.00 Chemical reaction & heat treatment method Sn/C-PANI 500 1000 522.00 82.87 Hydrogenated heat reduction method Graphene/Sn@C 400 500 506.00 81.81 Hydrolysis & pyrolysis method Sn/NC 200 400 630.00 87.21 Pyrolysis & Carbon Heat Reduction Method Sn/C 1000 150 690.00 96.00 Chemical reaction method Nano-sized Sn 320 150 375.61 90.32 Spray pyrolysis method Yolk-shell Sn@C microsphere 1000 500 691.00 68.45 Heat treatment method Sn/C 600 200 626.40 95.18 Carbonization treatment method 3D Sn@G-PGNWs 200 100 1089.00 85.76 Thermal polymerization & heat treatment method Sn-CS 300 100 440.00 96.24 Aerosol spray pyrolysis method Nano-Sn/C 200 130 692.15 96.52 Solid-liquid grinding/molding method Sn-GMC 100 100 560.00 80.99 Thermal polymerization & carbonization treatment method C/Sn 20 15 422.52 73.67 Heat reduction method GNS-Sn@CNT 100 100 982.00 84.47 Vapor-solid reaction method Sn@C core-shell NW 500 100 490.00 34.61 Heat reduction method Graphene/Sn/Graphene nanosheets 50 60 590.00 64.38 Hydrolysis & Heat Reduction Method RGO-Sn@C nanocables 50 50 630.00 69.86 Hydrothermal synthesis Sn/C 100 50 710.00 72.63 Electrospinning & heat treatment Sn@carbon@bamboo-like hollow carbon nanofibers 250 200 737.00 90.00 Reduction & heat treatment method Sn-CS 1000 200 522.34 93.44

Evaporation method Anode active material Rate characteristics Cut-off voltage
(V vs. Li/Li+) Current density
(mA g ^-One ) Reversible capacity
(mA g ^-One ) Thermal evaporation using RF plasma
Chemical vapor deposition (RF-PATE CVD) Sn-PC ₆₀ 10 000 544.33 0.01-3.00 Microwave solvent thermal synthesis method Ball-cactus-like Ni-Sn-P@C-CNT 5000 293.00 0.005-3.00 Settling & heat treatment method Sn@C nanoboxes 4000 350.00 0.005-3.00 Chemical reaction & heat treatment method Sn/C-PANI 5000 270.00 0.05-3.00 Hydrogenated heat reduction method Graphene/Sn@C 3200 270.00 0.001-3.00 Hydrolysis & pyrolysis method Sn/NC 5000 240.33 0.01-3.00 Pyrolysis & Carbon Heat Reduction Method Sn/C 2000 461.00 0.1-2.00 Chemical reaction method Nano-sized Sn 320 415.85 0.01-1.50 Spray pyrolysis method Yolk-shell Sn@C microsphere 8000 336.00 0.01-2.00 Heat treatment method Sn/C 6000 341.60 0.01-2.50 Carbonization treatment method 3D Sn@G-PGNWs 10 000 270.00 0.005-3.00 Thermal polymerization & heat treatment method Sn-CS 3000 220.60 0.00-2.50 Aerosol spray pyrolysis method Nano-Sn/C 7560 625.38 0.02-3.00 Solid-liquid grinding/molding method Sn-GMC 2000 330.00 0.005-2.00 Thermal polymerization & carbonization treatment method C/Sn 1000 305.24 0.02-1.50 Heat reduction method GNS-Sn@CNT 5000 594.00 0.005-3.00 Vapor-solid reaction method Sn@C core-shell NW 3000 286.00 0.005-2.00 Heat reduction method Graphene/Sn/Graphene nanosheets 1600 265.00 0.005-2.00 Hydrolysis & Heat Reduction Method RGO-Sn@C nanocables 1600 343.27 0.005-2.50 Hydrothermal synthesis Sn/C 1000 585.00 0.005-2.00 Electrospinning & heat treatment Sn@carbon@bamboo-like hollow carbon nanofibers 2500 480.00 0.01-3.00 Reduction & heat treatment method Sn-CS 6250 197.94 0.01-1.50

From the above description, those skilled in the art to which the present invention pertains will be able to understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential features thereof. In this regard, the embodiments described above are illustrative in all respects and should be understood as non-limiting. The scope of the present invention should be construed that all changes or modifications derived from the meaning and scope of the claims to be described later rather than the above detailed description, and equivalent concepts thereof, are included in the scope of the present invention.

Claims (13)

Including the step of polymerizing the tin precursor gas and fullerene using RF plasma,
The tin precursor gas is an organic compound containing tin,
The tin precursor gas is decomposed into tin particles (Sn) and tin having radicals and ionized tin by RF plasma,
The fullerene reacts with the decomposed tin precursor gas in an evaporated state to form a hierarchical structure of a tin (Sn)-tin oxide (SnO ₂ )-plasma polymerized fullerene (PC60) matrix, preparing a negative active material for a lithium secondary battery Way.
The method of claim 1, wherein the polymerization is performed through thermal evaporation chemical vapor deposition (RF-PATE CVD) using RF plasma.
The method of claim 1, wherein the polymerization is performed at an internal atmospheric pressure of 1.0x10 ^-9 to 1.0x10 ^-5 Torr and a current collector temperature of 200 to 300°C.
The method of claim 1, wherein the polymerization is performed at a carrier gas:tin precursor flow ratio of 8:1 to 1:3.
The method of claim 1, wherein the polymerization is performed at a radio frequency (RF) of 250 to 350 W.
The method of claim 1, wherein the polymerization is performed at a process pressure of 30 to 50 mTorr.
According to claim 1, wherein the tin precursor gas is tetrakis-dimethylaminotin (Sn[N(CH ₃ ) ₂ ] ₄ ) or tetramethyltin (Sn(CH ₃ ) ₄ ), which is a negative electrode for a lithium secondary battery Method of manufacturing an active material.
Tin (Sn) core-tin oxide (SnO ₂ ) core-shell-plasma polymerized fullerene (PC ₆₀ ) including a tin-fullerene complex (Sn-PC ₆₀ ; SPC) matrix structure,
Have the tin (Sn) core and the tin oxide (SnO ₂₎ SnO2 / PC60 interface between the Sn / SnO ₂ the interface between the core shell, the tin oxide (SnO ₂₎ core-shell and said plasma polymerized fullerene (PC ₆₀₎ ,
An ohmic resistance is formed at the Sn/SnO ₂ interface, and a pn semiconductor junction interface is formed at the SnO2/PC60 interface, a negative active material for a lithium secondary battery.
The negative active material for a lithium secondary battery according to claim 8, wherein the negative active material is prepared by the method of any one of claims 1 to 7.
The method of claim 8, wherein the composite is SPC-80 (Sn:PC ₆₀ =80:20 weight ratio), SPC-59 (Sn:PC ₆₀ =59:41 weight ratio), SPC-50 (Sn:PC ₆₀ =50: 50 weight ratio), SPC-41 (Sn:PC ₆₀ =41:59 weight ratio), or SPC-18 (Sn:PC ₆₀ =18:82 weight ratio), a negative electrode active material for a lithium secondary battery.
The negative active material for a lithium secondary battery according to claim 8, wherein the composite is characterized in that stress generated by repeated volume expansion and contraction is dispersed.
A negative electrode for a lithium secondary battery comprising the negative electrode active material for a lithium secondary battery of claim 8.
A lithium secondary battery comprising the negative active material for a lithium secondary battery of claim 8.

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