KR102331725B1 - Negative active material and lithium battery including the material - Google Patents

Abstract

Disclosed are an anode active material and a lithium battery employing the same. The negative active material includes a silicon-based alloy powder, the silicon-based alloy powder is silicon (Si); Among titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga) and germanium (Ge) The selected first metal (M ₁ ) and disposed on the inside and on the surface of the silicon-based alloy powder, carbon (C), boron (B), sodium (Na), nitrogen (N), phosphorus (P), sulfur (S) ) and chlorine (Cl) by including one or more additional elements (A) selected from, it may have a porosity inside the silicon-based alloy powder of 35% or less. Accordingly, the lifespan characteristics of a lithium battery employing the negative active material may be improved.

Description

Negative active material and lithium battery including the material

It relates to an anode active material and a lithium battery employing the same.

Lithium secondary batteries used in portable electronic devices for information and communication such as PDAs, mobile phones, and notebook computers, electric bicycles, and electric vehicles, exhibit a discharge voltage that is more than twice that of conventional batteries, resulting in high energy density. .

Lithium secondary batteries generate electricity by oxidation and reduction reactions when lithium ions are inserted/desorbed from the positive and negative electrodes in a state in which an organic electrolyte or polymer electrolyte is charged between the positive and negative electrodes including an active material capable of insertion and desorption of lithium ions. produce energy

As a positive active material of a lithium secondary battery, for example, lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or lithium nickel cobalt manganese oxide (Li[NiCoMn]O ₂ , Li[Ni _1-xy Co _{x )} An oxide composed of lithium and a transition metal having a structure capable of intercalation of lithium ions such as _{M y} ]O _{2 ) may be used.}

As an anode active material for a lithium secondary battery, various types of carbon-based materials including artificial, natural graphite, and hard carbon capable of inserting/deintercalating lithium, and non-carbon-based materials such as silicon (Si) are being studied.

The non-carbon-based material has a capacity density of 10 times or more compared to graphite, and can exhibit a very high capacity, but has poor electrical conductivity and a large volume change during lithium charging and discharging. Efficiency and lifetime characteristics may be degraded. Therefore, it is necessary to develop a high-performance negative active material with improved electrical conductivity and cycle life characteristics.

One aspect of the present invention is to provide an anode active material including an alloy powder having an internal porosity of 35% or less.

Another aspect of the present invention is to provide a lithium battery employing the negative active material.

In one aspect of the present invention,

As an anode active material comprising a silicon-based alloy powder,

The silicon-based alloy powder, silicon (Si); a first metal (M ₁ ); and an additive element (A); wherein the first metal (M ₁ ) is titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga) and germanium (Ge), wherein the additive element (A) is and carbon (C), boron (B), sodium (Na), nitrogen (N) , phosphorus (P), sulfur (S) and chlorine (Cl), and the additive element (A) is disposed on the inside and the surface of the silicon-based alloy powder, and the porosity inside the silicon-based alloy powder is 35% or less, wherein the porosity is provided as an anode active material represented by the following Equation 1:

<Equation 1>

.

.

According to one embodiment, the silicon-based alloy powder, the matrix including _{the silicon and the first metal (M 1 );} silicon nanoparticles dispersed in the matrix; and the additive element (A) disposed in the matrix and on the surface of the silicon-based alloy powder.

According to an embodiment, the matrix may _{include a compound phase including the Si and the first metal (M 1} ), and the silicon nanoparticles may include a single phase of Si.

According to an embodiment, at least a portion of the additive element (A) disposed in the matrix may be present in the form of silicide.

According to an embodiment, the first metal (M ₁ ) may be iron (Fe).

According to an embodiment, the silicon-based alloy powder may further include an oxygen (O) atom.

According to one embodiment, the silicon-based alloy powder, the silicon, the first metal (M ₁ ), and a matrix including oxygen (O) atoms; silicon nanoparticles dispersed in the matrix; and the additive element (A) disposed in the matrix and on the surface of the silicon-based alloy powder.

According to one embodiment, the matrix includes a compound phase consisting of the silicon and the first metal (M ₁ ) and a compound phase consisting of the silicon and the oxygen (O) atoms, and the silicon nanoparticles are It can include everyday life.

According to an embodiment, the matrix may _{further include a compound phase including the first metal (M 1} ) and the oxygen (O) atom.

According to one embodiment, the silicon-based powder alloy further comprises a second metal (M _2), the second metal (M ₂₎ is a manganese (Mn), yttrium (Y), zirconium (Zr), niobium (Nb ), molybdenum (Mo), silver (Ag), tin (Sn), tantalum (Ta), and tungsten (W) may be selected.

According to one embodiment, the silicon-based alloy powder is represented by Si-M ₁ -M ₂ -A,

The second metal (M ₂ ) is manganese (Mn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), silver (Ag), tin (Sn), tantalum (Ta), and tungsten (W) is selected from;

In the silicon-based alloy powder,

Based on the total number of atoms of the silicon, the first metal (M ₁ ), and the second metal (M ₂ ), the content of Si is 50 to 90 atomic%, the first metal (M ₁ ) The content is 10 atomic% to 50 atomic%, the _{content of the second metal (M 2} ) is 0 atomic% to 10 atomic%,

Based on 100 parts by weight of the sum of the silicon, the first metal (M ₁ ) and the second metal (M ₂ ), the total content of the additive element (A) is 0.01 parts by weight to 20 parts by weight,

The total content of the additive element (A) may be the sum of the content of the additive element (A) disposed inside the silicon-based alloy powder and the content of the additive element (A) disposed on the surface.

According to one embodiment, based on 100 parts by weight of the sum of the silicon, the first metal (M ₁ ), and the second metal (M ₂ ), the total content of the additive element (A) is 1 part by weight to 9 parts by weight can be negative

According to an embodiment, the content of the additive element (A) disposed on the surface of the silicon-based alloy powder may be greater than or equal to the content of the additive element (A) included in the silicon-based alloy powder.

According to one embodiment, the content of the additive element (A) disposed inside the silicon-based alloy powder is based on 100 parts by weight of the sum _{of the silicon, the first metal (M 1} ) and the second metal (M _{2 ),} 0.1 parts by weight to 4 parts by weight;

The content of the additive element (A) disposed on the surface of the silicon-based alloy powder is 0.5 parts by weight to 7 parts by weight based on 100 parts by weight of the sum _{of the silicon, the first metal (M 1} ), and the second metal (M _{2 )} It may be parts by weight.

According to one embodiment, the silicon-based alloy powder is represented by Si-M ₁ -M ₂ -AO,

The second metal (M ₂ ) is manganese (Mn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), silver (Ag), tin (Sn), tantalum (Ta), and tungsten (W) is selected from;

In the silicon-based alloy powder,

Based on the total number of atoms of the silicon, the first metal (M ₁ ) and the second metal (M ₂ ), the content of Si is 50 to 90 atomic%, and the content of _{the first metal (M 1 )} This 10 atomic % to 50 atomic %, the _{content of the second metal (M 2} ) is 0 to 10 atomic %,

Based on 100 parts by weight of the sum of the silicon, the first metal (M ₁ ) and the second metal (M ₂ ), the total content of the additive element (A) is 0.01 parts by weight to 20 parts by weight, and the oxygen (O ) may be in an amount of 0.01 parts by weight to 50 parts by weight.

According to one embodiment, the silicon-based alloy powder,

a matrix comprising the silicon, the first metal (M ₁ ), the second metal (M ₂ ), and oxygen (O) atoms;

silicon nanoparticles dispersed in the matrix; and

has a structure comprising; the additive element (A) disposed in the matrix and on the surface of the silicon-based alloy powder,

The matrix includes a compound phase consisting of the silicon and the first metal (M ₁ ), a compound phase consisting of the silicon and the second metal (M ₂ ), and a compound phase consisting of the silicon and the oxygen (O) atoms do,

The silicon nanoparticles may include a single phase of the silicon.

According to one embodiment, the silicon-based alloy powder is represented by Si-M ₁ -M ₂ -CBO,

The second metal (M ₂ ) is manganese (Mn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), silver (Ag), tin (Sn), tantalum (Ta), and tungsten (W) is selected from;

In the silicon-based alloy powder,

Based on the total number of atoms of the silicon, the first metal (M ₁ ) and the second metal (M ₂ ), the content of Si is 50 to 90 atomic%, and the content of _{the first metal (M 1 )} This 10 atomic % to 50 atomic %, the _{content of the second metal (M 2} ) is 0 to 10 atomic %,

Based on 100 parts by weight of the sum of the silicon, the first metal (M ₁ ), and the second metal (M ₂ ), the total content of C is 1 to 9 parts by weight, and the total content of B is 0 The amount of O may be in the range of from 0.01 parts by weight to 20 parts by weight, and the content of O may be in the range of 0.01 parts by weight to 50 parts by weight.

According to an embodiment, the average particle diameter (D50) of the silicon-based alloy powder may be 1 μm to 5 μm.

According to an embodiment, the average particle diameter (D50) of the silicon nanoparticles may be 10 nm to 150 nm.

In another aspect of the present invention, a lithium battery including the negative active material is provided.

The anode active material may include a silicon-based alloy powder having a porosity of 35% or less in the alloy powder, thereby improving electrical conductivity and lifespan characteristics of a lithium battery employing the anode active material.

1 is a schematic diagram showing the structure of a lithium battery according to an embodiment.
2 is a measurement result of porosity inside the alloy powder prepared in Examples 1 to 7;
3 is a scanning electron microscope (SEM) photograph (1000 magnification) of the inner cross-section of the alloy powder prepared in Example 1.
4 to 6 are SEM photographs (3000 magnification) of the inner cross-section of the alloy powder prepared in Examples 3 to 5, respectively.
7 is a SEM photograph (3000 magnification) of the inner cross section of the alloy powder prepared in Comparative Example 1.
8 is a transmission electron microscope (TEM) photograph (130,000 magnification) of the inside of the alloy powder prepared in Example 1. FIG.
9 is a high angle annular dark field-scanning transmission electron microscope (HAADF-STEM) analysis photograph (150,000 magnification) of the inside of the alloy powder prepared in Example 14;
10 is an H AADF-STEM analysis photograph (350,000 magnification) of a portion of FIG. 9 .
11 is an EDX analysis result for each element C, O, Si and Fe along the solid line of FIG. 10 .
12 is an XPS analysis result of the alloy powder prepared in Examples 4, 8 and 9.
13 is a TEM photograph (530,000 magnification) of the inside of the alloy powder before and after charging and discharging 100 times of the lithium secondary battery prepared in Example 1.
14 is a view showing the capacity retention rate for each cycle of the lithium secondary batteries prepared in Examples 1 to 5 and Comparative Example 1. Referring to FIG.
15 is a view showing the capacity retention rate for each cycle of the lithium secondary batteries prepared in Examples 14 to 16 and Comparative Examples 1 to 3;

Hereinafter, the present invention will be described in more detail. In embodiments of the present invention, atomic percent (at%) represents the number of atoms occupied by a corresponding component in the total number of atoms of the entire material as a percentage.

The negative active material according to one aspect,

Containing a silicon-based alloy powder,

The silicon-based alloy powder,

silicon (Si); a first metal (M ₁ ) and an additive element (A);

The first metal (M ₁ ) is titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga) and germanium (Ge),

The additive element (A) is one or more selected from carbon (C), boron (B), sodium (Na), nitrogen (N), phosphorus (P), sulfur (S) and chlorine (Cl),

The additive element (A) is disposed on the inside and the surface of the silicon-based alloy powder,

The porosity inside the silicon-based alloy powder is 35% or less.

The "silicon-based" alloy powder means containing at least about 50 atomic% of silicon (Si) based on the total number of atoms of the alloy powder. Since the negative active material includes the silicon-based alloy powder, a battery having a higher capacity than that of the carbon-based negative active material may be realized.

However, during charging and discharging of a lithium secondary battery, the silicon expands/contracts in volume due to intercalation/deintercalation of lithium, and as the change in volume is repeated, cracks may be formed on the surface of the anode active material, The cycle characteristics of the lithium battery may be deteriorated by such cracks.

In addition, in the case of an alloy powder formed through alloying of silicon and various metals, there are voids inside the powder. When the proportion of voids in the powder is high, an irreversible side reaction product may be formed during charging and discharging due to side reactions between silicon and/or metal and the electrolyte. Cycle characteristics of the lithium secondary battery may be deteriorated by these side reactants.

In order to overcome the above problems, the inventors of the present invention have completed a silicon-based alloy powder having an internal porosity of 35% or less by including the additive element (A) on both the inner and outer surfaces of the silicon-based alloy powder. At this time, the porosity inside the silicon-based alloy powder not containing the additive element (A) is greater than 35%.

The additive element (A) included in the silicon-based alloy powder may serve as a buffer layer for buffering a volume change of silicon and to reduce the porosity inside the silicon-based alloy powder. Specifically, the additive element (A) may be located inside the silicon-based alloy powder, suppressing the expansion of silicon during charging of the lithium battery, and reducing side reaction sites with the electrolyte. In addition, the additive element (A) disposed on the outer surface of the silicon-based alloy powder may serve as a double buffer layer for volume expansion of silicon, and may reduce consumption of lithium due to a side reaction with an additional electrolyte.

Accordingly, when the additive element (A) is included in both the inner and outer surfaces of the silicon-based alloy powder, the capacity and lifespan characteristics of the lithium battery may be improved.

Meanwhile, in the present specification, the silicon-based "porosity inside the alloy powder" may be expressed by the following Equation 1:

<Equation 1>

.

.

The porosity inside the alloy powder represented by Equation 1 is distinct from the porosity between the powders or the total porosity (the ratio of the sum of the voids inside the powder and the voids between the powders in the total volume), and is present in the powder It is a figure that considers only the voids.

The "density (g/cc) of the powder measured at a pressure of 20 kN" in Equation 1 is the (a certain amount of the powder) when (pressing) (pressing) at a pressure of 20 kN (which occupies a certain amount of the powder) It corresponds to the value divided by the volume) and can be measured using a conductivity measuring device, etc. At this time, the measured density value has a smaller value than the actual powder density because it is calculated by including the voids inside the alloy powder under a pressure of 20 kN.

The "true density (g/cc) of the powder" in Equation 1 corresponds to a value obtained by dividing (a certain amount of the powder) by (the volume occupied by a certain amount of the powder, excluding the pores inside the powder), and the gas peak It can be measured using a normometer.

According to one embodiment, the porosity inside the silicon-based alloy powder may be 20% to 35%. For example, the porosity in the silicon-based alloy powder may be 20% to 32%. Specifically, for example, the porosity in the silicon-based alloy powder may be 20% to 30%, more specifically, for example, 24% to 30%. In the above range, while the side reaction with the electrolyte is suppressed, the initial efficiency of the battery may not be reduced due to a decrease in the impregnation property of the electrolyte.

Here, the porosity inside the silicon-based alloy powder can be adjusted by the content of the additive element (A). Specifically, even when the content of the additive element (A) is the same, the porosity may be adjusted by adjusting the content of the additive element (A) disposed inside the silicon-based alloy powder. For example, when the content of the additive element (A) disposed inside the silicon-based alloy powder is increased, the porosity inside the alloy powder may be reduced. Conversely, when the content of the additive element (A) disposed inside the silicon-based alloy powder is reduced, the porosity inside the alloy powder may be increased. The content of the additive element (A) disposed in the silicon-based alloy powder may be adjusted by varying the input time or process time of the raw material including the additive element (A) during the alloy manufacturing process. According to one embodiment, The first metal (M ₁ ) may be iron (Fe), Al, or Cu. For example, the first metal (M ₁ ) may be iron (Fe). When the first metal (M ₁ ) is iron (Fe), volume expansion of silicon may be effectively suppressed.

According to an embodiment, the silicon-based alloy powder may include: a matrix including _{the silicon and the first metal (M 1 );} silicon nanoparticles dispersed in the matrix; and the additive element (A) disposed in the matrix and on the surface of the silicon-based alloy powder.

The matrix including the silicon and the first metal (M ₁ ) is an inert matrix that does not intercalate/deintercalate lithium ions during charging and discharging of a lithium battery, and serves to suppress volume expansion of the silicon-based alloy powder. can be performed.

According to an embodiment, the matrix may include a compound phase composed of the inactive Si and the first metal (M _{1 ).} For example, the compound phase made of Si and the first metal (M ₁ ) may include a first metal (M ₁ ) silicide.

For example, when the first metal (M ₁ ) is Fe, the compound phase composed of Si and the first metal (M ₁ ) is a FeSi phase, FeSi ₂ phase, or Fe ₂ Si ₅ phase.

For example, when the first metal (M ₁ ) is Fe, the compound phase consisting of Si and the first metal (M _{1 ) is FeSi 2} phase, for example FeSi ₂ a beta phase or a Fe ₂ Si ₅ alpha phase, for example a Fe ₂ Si ₅ alpha phase. The FeSi ₂ phase is a peak, diffraction angle ( 2θ) a peak for the crystal plane 101 at 38.0 +/- 0.5 degrees (˚), and/or a peak for the crystalline plane (001) at 17.3 +/- 0.5 degrees (˚) at a diffraction angle (2θ). When the FeSi ₂ phase is included in the matrix of the alloy powder, volume expansion of silicon nanoparticles during charging and discharging of a lithium battery is suppressed, and lifespan characteristics of a lithium battery can be improved.

When the first metal (M ₁ ) is Al, the compound phase composed of Si and the first metal (M _{1 ) may include an Al 3} Si ₃ phase.

When the first metal (M ₁ ) is Cu, the compound phase including Si and the first metal (M ₁ ) may include a Cu ₃ Si phase. For example, when the first metal (M ₁ ) is Cu, the compound phase composed of Si and the first metal (M ₁ ) may be a _{Cu 3 Si phase.}

Meanwhile, the silicon nanoparticles may include a single phase of the silicon. For example, the single phase of silicon is a phase made of only silicon, and may include active silicon capable of reversible reaction with lithium ions, which determines the capacity of a silicon-based alloy.

The Si single phase may exhibit a peak with respect to the crystal plane 111 at a diffraction angle (2θ) of 28.5 +/- 0.5 degrees (˚) of an X-ray diffraction spectrum using Cu-Kα.

The additive element (A) disposed on the surface of the alloy powder may be continuously disposed on the surface of the alloy powder or may be disposed discontinuously in an island type. Here, the "island" type means a spherical, hemispherical, non-spherical, or atypical shape having a predetermined volume, and the shape is not particularly limited. The additive element (A) disposed on the surface of the alloy powder may exist in a state in which it is not combined with other materials.

The additive element (A) disposed in the alloy powder may be present in the matrix. Specifically, the additive element (A) disposed in the alloy powder may be present between the matrix and the silicon nanoparticles. For example, the additive element (A) may be located in voids that may exist in the absence of the additive element (A), thereby reducing voids in the matrix of the alloy powder. Accordingly, the porosity inside the silicon-based alloy powder may be adjusted to 35% or less by the addition of the additive element (A).

According to one embodiment, at least a portion of the additive element (A) disposed in the alloy powder may be present in the form of a silicide, for example, in the form of a compound consisting of the additive element (A) and silicon. For example, the additive element (A) may react with silicon during the alloy powder manufacturing process to form the silicide, and the formed silicide may exist in the matrix.

According to an embodiment, the additive element (A) may be boron and/or carbon.

For example, when the additive element (A) is boron, at least a portion of the boron in the alloy powder is SiB ₄ , SiB ₆ silicides, etc., with the remainder being B.

For example, when the additive element (A) is carbon, at least a portion of carbon in the alloy powder may be a silicide such as SiC, and the remainder may be present as C. In this case, C may be amorphous carbon.

The carbon has a Mohs hardness of about 1-2 lower than that of Si(6-7) and Fe(4), so that when the silicon-based alloy powder is manufactured, voids present in the alloy powder can be effectively filled. In addition, carbon present on the surface of the alloy powder may contribute to the improvement of the electrical conductivity of the negative electrode.

According to an embodiment, the silicon-based alloy powder may further include an oxygen (O) atom. For example, the oxygen (O) atoms may form a matrix together _{with the silicon and the first metal (M 1 ).} Specifically, when the silicon-based alloy powder further includes oxygen (O) atoms, the matrix of the silicon-based alloy powder may further include a compound phase consisting of silicon and oxygen (O) atoms. The compound phase composed of silicon and oxygen (O) atoms may be an oxide phase such as _{SiO 2 .}

According to an embodiment, the compound phase consisting of silicon and oxygen (O) atoms _{is present at the interface between the compound phase consisting of silicon and the first metal (M 1} ) and silicon nanoparticles, increasing the density of the matrix to reduce the porosity can play a role in making

According to one embodiment, when the silicon-based alloy powder further contains oxygen (O) atoms, the matrix of the silicon-based alloy powder is the first metal (M ₁ ) in addition to the compound phase consisting of silicon and oxygen (O) atoms. and a compound phase composed of the oxygen (O) atoms. For example, the compound phase consisting of the first metal (M ₁ ) and the oxygen (O) atom may be an oxide, and when the compound phase consisting of the first metal (M ₁ ) and the oxygen (O) atom exists, the It can play the same role as the compound phase consisting of silicon and oxygen (O) atoms.

According to another embodiment, the silicon-based alloy powder may further include a second metal (M _2), the second metal (M ₂₎ is a manganese (Mn), yttrium (Y), zirconium (Zr), niobium It may be selected from (Nb), molybdenum (Mo), silver (Ag), tin (Sn), tantalum (Ta), and tungsten (W).

When the silicon-based alloy powder _{further includes a second metal (M 2} ), the matrix may further include a compound phase made of the silicon and the second metal (M _{2 ).} Due to the compound phase consisting of the silicon and the second metal (M ₂ ), the volume expansion of the silicon nanoparticles can be more effectively buffered.

According to an embodiment, the silicon-based alloy powder may be represented by _{Si-M 1} -M _{2 -A.}

In the silicon-based alloy powder, the content of Si is 50 to 90 atomic%, for example, based on the total number of atoms of _{the silicon, the first metal (M 1} ) and the second metal (M _{2 )} , may be 70 atomic% to 90 atomic%, and in the silicon-based alloy powder, the _{content of the first metal (M 1} ) may be 10 atomic% to 50 atomic%, for example, 10 atomic% to 30 atomic% have. Within the above range, desired levels of discharge capacity and lifespan characteristics may be realized.

In the silicon-based alloy powder, the second metal (M ₂₎ content, based on the total number of the silicon, the first metal (M ₁₎ and the second metal (M ₂₎ atoms, 0 atom% to 10 It may be atomic %, for example from 0 atomic % to 5 atomic %.

In the silicon-based alloy powder, the total content of the additive element (A) is 0.01 parts by weight to 20 parts by weight based on 100 parts by weight of the sum _{of the silicon, the first metal (M 1} ), and the second metal (M _{2 )} can be negative Here, the total content of the additive element (A) means the sum of the content of the additive element (A) disposed inside the silicon-based alloy powder and the content of the additive element (A) disposed on the surface. In the above range, while the porosity inside the alloy powder is adjusted to 35% or less, the lifespan characteristics of the lithium battery may be improved. For example, in the silicon-based alloy powder, the total content of the additive element (A) is 1 weight based on 100 parts by weight of the sum _{of the silicon, the first metal (M 1} ), and the second metal (M _{2 )} parts to 9 parts by weight, for example, 2 parts by weight to 9 parts by weight.

According to one embodiment, based on 100 parts by weight of the sum of the silicon, the first metal (M1) and the second metal (M2), the content of the additive element (A) included in the silicon-based alloy powder is 0.1 parts by weight to 4 parts by weight, and the content of the additive element (A) disposed on the surface of the silicon-based alloy powder may be 0.5 parts by weight to 7 parts by weight. Within the above range, the capacity and lifespan characteristics of the lithium battery may be further improved.

The content of the additive element (A) contained in the silicon-based alloy powder and the content of the additive element (A) disposed on the surface of the silicon-based alloy powder may be measured using a thermogravimetric analyzer (TGA). Specifically, when heat of 400° C. to 500° C. is applied to a certain amount of the silicon-based alloy powder, the additive element (A) disposed on the surface of the silicon-based alloy powder reacts with oxygen in the atmosphere and is oxidized, so that on the surface of the silicon-based alloy powder A weight reduction occurs in the initial weight of the silicon-based alloy powder by the amount of the additive element (A) disposed in the . Accordingly, the weight reduced from the initial weight of the silicon-based alloy powder corresponds to the content of the additive element (A) disposed on the surface of the silicon-based alloy powder. Then, when the content of the additive element (A) disposed on the surface of the silicon-based alloy powder is subtracted from the total content of the additive element (A) (the amount of the additive element (A) in the production of the silicon-based alloy powder), the silicon-based alloy powder The content of the additive element (A) contained in it can be obtained.

According to another embodiment, the silicon-based alloy powder may be represented by _{Si-M 1} -M _{2 -AO.}

In the silicon- _{based alloy powder represented by Si-M 1} -M ₂ -AO, the content of Si, the content of the first metal (M ₁ ), the content of the second metal (M ₂ ), and the additive element (A) ) is the same as described above,

The content of the oxygen (O) atom is 0.01 parts by weight to 50 parts by weight, for example, 0.1 parts by weight based on 100 parts by weight of the sum _{of the silicon, the first metal (M 1} ) and the second metal (M _{2 )} It may be in an amount of from 20 parts by weight to 20 parts by weight. Oxygen atoms in the above range may be present in the form of compounds with silicon and/or metals, contributing to reducing the porosity without reducing the capacity of the alloy powder.

According to another embodiment, the silicon-based alloy powder may be represented by _{Si-M 1} -M _{2 -CBO.}

In the silicon- _{based alloy powder represented by the Si-M 1} -M ₂ -CBO, the content of Si, the content of the first metal (M ₁ ), the content of the second metal (M ₂ ), and the oxygen (O) The content of atoms is as described above,

The total content of C is 0.01 parts by weight to 20 parts by weight based on 100 parts by weight of the sum of the silicon, the first metal (M ₁ ), and the second metal (M _{2 ), and the total content of B is 0} It may be in an amount of from 20 parts by weight to 20 parts by weight. Here, the total content of C and the total content of B mean the sum of the contents of C and B disposed inside and on the surface of the silicon-based alloy powder, respectively. In the above range, the porosity inside the silicon-based alloy powder may be adjusted to 35% or less.

For example, the total content of C is 0.1 parts by weight to 10 parts by weight, specifically, based on 100 parts by weight of the sum _{of the silicon, the first metal (M 1} ) and the second metal (M _{2 )} For example, it may be 1 part by weight to 9 parts by weight, more specifically, for example, 2 parts by weight to 9 parts by weight.

In addition, the total content of B is 0 parts by weight to 10 parts by weight, specifically, based on 100 parts by weight of the sum _{of the silicon, the first metal (M 1} ) and the second metal (M _{2 ), for example,} It may be 0 parts by weight to 5 parts by weight, more specifically, for example, 0.1 parts by weight to 5 parts by weight.

According to an embodiment, the average particle diameter (D50) of the silicon-based alloy powder may be 1 μm to 5 μm. For example, the average particle diameter (D50) of the silicon-based alloy powder may be 1 μm to 3 μm. Specifically, for example, the average particle diameter (D50) of the silicon-based alloy powder may be 2 μm to 3 μm.

Here, “D50” refers to a particle diameter corresponding to 50% from the smallest particle when the total number of particles is 100% in the distribution curve accumulated in the order of the smallest particle to the largest particle. D50 may be measured by a method well known to those skilled in the art, for example, it may be measured with a particle size analyzer, or may be measured from a TEM (Transmission electron microscopy) or SEM (Scanning electron microscopy) photograph. As an example of another method, after measuring using a measuring device using dynamic light-scattering, data analysis is performed to count the number of particles for each size range, and from this, D50 is calculated easy to get

According to an embodiment, the average particle diameter (D50) of the silicon nanoparticles may be 10 nm to 150 nm. For example, the particle size of the silicon nanoparticles may be 10 nm to 100 nm, or 10 nm to 50 nm.

Since the active silicon nanoparticles having a particle size in the above range are evenly distributed in the inert matrix, volume expansion of the active silicon nanoparticles during a charge/discharge cycle can be efficiently buffered by the inert matrix surrounding them.

The D50 of the silicon nanoparticles was determined using the half width of the peak for the crystal plane 111 at the diffraction angle (2θ) 28.5 +/- 0.5 degrees (˚) of the X-ray diffraction analysis spectrum using Cu-Kα of the Si single phase. It can be obtained from Scherrer's equation.

The negative active material may include the above-described silicon-based alloy powder as an essential component and further include an anode active material commonly used in lithium batteries in addition to the essential component.

As the negative active material material, graphite capable of occluding and releasing lithium ions, a carbon-based material such as carbon, lithium metal, an alloy thereof, a silicon oxide-based material, a mixture thereof, and the like may be used.

According to one embodiment, a silicon-based alloy and a carbon-based material are used as the negative active material, and the carbon-based material is natural graphite, artificial graphite, expanded graphite, graphene, carbon black, fullerene soot, carbon nanotube. , carbon fiber, soft carbon hard carbon, pitch carbide, mesophase pitch carbide, calcined coke, etc. may be used, and two or more of these may be used in combination.

In this way, when the carbon-based material is used together, the oxidation reaction of the silicon-based alloy is suppressed, and a solid electrolyte interphase (SEI) film is effectively formed to form a stable film, and the electric conductivity is improved, thereby further improving the charging and discharging characteristics of lithium. .

When the carbon-based material is used, for example, the carbon-based material may be mixed and blended with a silicon-based alloy or used in a state coated on the surface of the silicon-based alloy.

The content of the negative active material used together with the silicon-based alloy may be 1 to 99% by weight based on the total content of the silicon-based alloy and the negative active material.

When the silicon-based alloy powder is a major component in the anode active material, the content of the silicon-based alloy may be, for example, 95 to 99 wt% based on the total content of the anode active material and the silicon-based alloy. When the pitch of graphite or amorphous carbon is used as the negative active material material, the pitch of graphite or amorphous carbon may be coated on the surface of the silicon-based alloy.

When the silicon-based alloy powder is a minor component in the anode active material, the content of the silicon-based alloy may be, for example, 1 to 5 wt% based on the total content of the anode active material and the silicon-based alloy. When a pitch of graphite or amorphous carbon is used as the anode active material, the pitch of graphite or amorphous carbon serves as a buffer of the silicon-based alloy, and thus the lifespan of the electrode may be further improved.

Hereinafter, a method of manufacturing an anode active material including the silicon-based alloy powder will be described.

According to one embodiment, the method of manufacturing the negative active material,

a mother alloy having a composition of 50 atomic % to 90 atomic % Si, 10 atomic % to 50 atomic % of a first metal (M ₁ ), and optionally 0 atomic % to 10 atomic % of a second metal (M _{2 );} manufacturing;

quick-solidifying the melt of the master alloy to obtain a quench-solidifying alloy; and

Grinding the quench-solidified alloy to prepare a silicon-based alloy powder; includes, in this case, carbon (C), boron (B), sodium (Na), nitrogen (N), phosphorus (P), sulfur (S) ) and chlorine (Cl) in the step of preparing a silicon-based alloy powder by pulverizing the material containing at least one additive element (A) selected from the group consisting of the mother alloy and / or the quench-solidified alloy, the manufactured The content of the additive element (A) inside and on the surface of the silicon-based alloy powder is the amount of the additive element (A) based on 100 parts by weight of the sum _{of the silicon, the first metal (M 1} ) and the second metal (M _{2 )} It may be added so that the total content is 0.01 parts by weight to 20 parts by weight.

For example, the additive element (A)-containing material may be added in the step of preparing the silicon-based alloy powder by pulverizing the quench-solidified alloy.

The content of the additive element (A) in the silicon-based alloy powder may be adjusted by changing the timing of adding the additive element (A)-containing material. For example, the additive element (A)-containing material may be added during pulverization of the quench-solidified alloy so that the additive element (A) is disposed on the surface rather than inside the silicon-based alloy powder. For example, the additive element (A)-containing material may be added after half of the total grinding time of the quench-solidification alloy has elapsed. Specifically, for example, the additive element (A)-containing material may be added after 3/4 of the total grinding time of the quench-solidification alloy has elapsed. By the above method, the content of the additive element (A) disposed on the surface is equal to or greater than the content of the additive element (A) contained therein, for example, the content of the additive element (A) disposed on the surface is added to the inside. A silicon-based alloy powder having 2 to 4 times the content of the included additive element (A) may be prepared.

According to an embodiment, when the additive element (A) is boron, the added element (A)-containing material may be boric acid. Specifically, for example, it may be boric acid having a layered structure. Alternatively, the added element (A)-containing material may be selected from among M ₂ B (M=Ta, Mo, W, Mn, Fe, Co, or Ni) and M ₃ B ₄ (M=Nb, Ta, Cr or Mn) compounds. can be selected.

According to another embodiment, when the additive element (A) is carbon, the added element (A)-containing material may be crystalline carbon, amorphous carbon, or a mixture thereof. For example, the crystalline carbon is amorphous, plate-like, flake-like, spherical or fibrous, graphite such as natural graphite and artificial graphite, carbon black, carbon whisker (carbon whisker), at least one selected from pitch-based carbon fiber, and the amorphous carbon may be selected from one or more of soft carbon and hard carbon. Specifically, for example, when the additive element (A) is carbon, the added element (A)-containing material may be flaky natural graphite or artificial graphite.

On the other hand, an oxygen atom-containing material may be added in the step of preparing the master alloy and/or grinding the quench-solidified alloy to prepare a silicon-based alloy powder so that the silicon-based alloy powder further contains oxygen (O) atoms. have. Examples of the oxygen atom-containing material include, but are not limited to _{, Fe 2} O ₃ , SiO _{2 , SiO, and the like.} Alternatively, the silicon-based alloy powder prepared by mixing oxygen in the atmosphere during the process may further include oxygen atoms. Alternatively, by treating in an oxygen atmosphere during the process, the silicon-based alloy powder prepared above may further include oxygen atoms.

The step of preparing the master alloy may include a vacuum induction melting method (VIM), an arc melting method, or a mechanical alloying method, for example, to suppress oxidation by the atmosphere as much as possible. For this purpose, a vacuum induction melting method for dissolving the master alloy in a vacuum atmosphere may be used. However, the method is not limited to the method for preparing the master alloy, and any method capable of producing the master alloy that can be used in the art may be used.

The form of the raw material for producing the silicon-based alloy powder is not particularly limited as long as the required composition ratio can be realized. For example, in order to mix the elements constituting the silicon-based alloy in a desired composition ratio, an element, an alloy, a solid solution, an intermetallic compound, or the like may be used.

For example, after the metal powder of each element is weighed and mixed at a target alloy composition ratio, a mother alloy of a silicon-based alloy may be manufactured using a vacuum induction melting furnace. Vacuum induction melting furnace is an equipment that can melt metals with high melting temperature through high-frequency induction. In the initial melting step, after the inside of the vacuum induction melting furnace is made into a vacuum state, an inert gas such as Ar is injected into the vacuum induction melting furnace to prevent or reduce oxidation of the prepared master alloy.

Next, the mother alloy prepared as above is melted, and the melt is rapidly cooled and solidified. The rapid solidification process is not particularly limited, but may be performed, for example, by a melt spinning method, a gas atomize method, or a strip cast method. Through the rapid solidification process, an alloy in which silicon nanoparticles are evenly dispersed in the matrix may be formed.

The rapid solidification process may be performed by a melt spinning method. For example, the melt of the master alloy can be rapidly cooled and solidified while being injected into a wheel rotating at high speed through a melt spinner equipment using high-frequency induction. In this case, the rapid solidification may include rapidly cooling the melt of the master alloy at a rate of 10 ³ K/sec to 10 ⁷ K/sec.

master alloy Since the melt is cooled by a wheel rotating at a high speed, it is injected in the shape of a ribbon, and the shape of the ribbon and the size of silicon nanoparticles distributed in the alloy depend on the cooling rate. In order to obtain fine silicon nanoparticles, it may be cooled, for example, at a cooling rate of about 1000° C./s or more. In addition, in order to obtain uniform silicon nanoparticles, the thickness of the injection molding in the form of a ribbon can be adjusted, for example, in the range of 5 to 20 μm, and more specifically, it is preferable to form the ribbon thickness in the range of 7 to 16 μm.

As such, the rapid-solidification alloy, which is an alloy injection product in the form of a ribbon formed by rapid cooling and solidification, is pulverized into a powder to be used as an anode active material. The pulverized alloy powder may have a D50 in the range of 1 μm to 5 μm. The grinding technique may be performed by a method commonly used in the art. For example, the device used for grinding is not limited thereto, but an atomizer, a vacuum mill, a ball mill, a planetary ball, a beads mill, a jet and jet mills. The pulverization may be performed for 6 hours to 48 hours.

Grinding methods are broadly classified into dry grinding and wet grinding, and either method is possible.

A lithium battery according to another aspect includes an anode including the anode active material described above. For example, a lithium battery according to an embodiment includes an anode including the anode active material; an anode disposed to face the cathode; and an electrolyte disposed between the negative electrode and the positive electrode.

The negative electrode and the lithium battery including the same may be manufactured by the following method.

The negative electrode includes the negative electrode active material described above, and for example, the negative electrode active material composition is prepared by mixing the negative electrode active material, the binder, and optionally a conductive material in a solvent, and then forming the negative electrode active material composition into a predetermined shape or using a copper foil. ) can be prepared by applying to the current collector, such as.

The binder used in the negative active material composition is a component that assists in bonding the negative active material and the conductive material and the like to the current collector, and is added in an amount of 1 to 50 parts by weight based on 100 parts by weight of the negative electrode active material. For example, the binder may be added in an amount of 1 to 30 parts by weight, 1 to 20 parts by weight, or 1 to 15 parts by weight based on 100 parts by weight of the negative active material. Examples of such binders include polyvinylidene fluoride, polyvinylidene chloride, polybenzimidazole, polyimide, polyvinyl acetate, polyacrylonitrile, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydro Roxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polystyrene, polymethyl methacrylate, polyaniline, acrylonitrile-butadiene styrene, phenol resin, epoxy resin, polyethylene Terephthalate, polytetrafluoroethylene, polyphenylsulfide, polyamideimide, polyetherimide, polyethylenesulfone, polyamide, polyacetal, polyphenylene oxide, polybutylene terephthalate, ethylene-propylene-diene ether polymer (EPDM) ), sulfonated EPDM, styrene butadiene rubber, fluororubber, and various copolymers.

The negative electrode may optionally further include a conductive material in order to further improve electrical conductivity by providing a conductive path to the negative electrode active material described above. As the conductive material, any one generally used in lithium batteries may be used, and examples thereof include carbon-based materials such as carbon black, acetylene black, ketjen black, and carbon fibers (eg, vapor-grown carbon fibers); metal-based substances such as metal powders such as copper, nickel, aluminum, and silver, or metal fibers; A conductive material including a conductive polymer such as a polyphenylene derivative or a mixture thereof can be used. The content of the conductive material may be appropriately adjusted and used. For example, a weight ratio of the negative active material and the conductive material may be added in a range of 99:1 to 90:10.

As the solvent, N-methylpyrrolidone (NMP), acetone, water, etc. may be used. The amount of the solvent is 1 to 10 parts by weight based on 100 parts by weight of the negative active material. When the content of the solvent is within the above range, the operation for forming the active material layer is easy.

In addition, the current collector is generally made to a thickness of 3 to 500 ㎛. The current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface. Carbon, nickel, titanium, one surface-treated with silver, an aluminum-cadmium alloy, etc. may be used. In addition, the bonding strength of the negative electrode active material may be strengthened by forming fine irregularities on the surface, and may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam body, and a nonwoven body.

A negative electrode plate can be prepared by directly coating the prepared negative electrode active material composition on a current collector, or a negative electrode plate can be obtained by casting a negative electrode active material film on a separate support and laminating the negative electrode active material film peeled from the support on a copper foil collector. The negative electrode is not limited to the above-mentioned types and may be of a type other than the above-mentioned types.

The anode active material composition is not only used for manufacturing an electrode of a lithium battery, but also printed on a flexible electrode substrate to be used for manufacturing a printable battery.

Separately, a positive electrode active material composition in which a positive electrode active material, a conductive material, a binder, and a solvent are mixed in order to manufacture a positive electrode is prepared.

As the cathode active material, any material commonly used as a cathode active material in the art may be used. For example, Li _a A _{1 - b} B _b D ₂ (wherein 0.90 ≤ a ≤ 1, and 0 ≤ b ≤ 0.5); _{Li a E 1 - b B b} O 2 - ( in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05) c D c; LiE _{2 - b} B _b O _{4 - c} D _c (wherein 0 ≤ b ≤ 0.5 and 0 ≤ c ≤ 0.05); Li _a Ni _{1 -b- c} Co _b B _c D _α (wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li _a Ni _{1 -b- c} Co _b B _c O _{2 -α} F _α (where 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _{1 -b- c} Co _b B _c O _{2 -α} F ₂ (wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _{1 -b- c} Mn _b B _c D _α (wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li _a Ni _{1 -b- c} Mn _b B _c O _{2 -α} F _α (where 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _{1 -b- c} Mn _b B _c O _{2 -α} F ₂ (wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _b E _c G _d O ₂ (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li _a Ni _b Co _c Mn _d GeO ₂ (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li _a NiG _b O ₂ (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li _a CoG _b O ₂ (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li _a MnG _b O ₂ (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li _a Mn ₂ G _b O ₄ (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); QO ₂ ; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiIO ₂ ; LiNiVO ₄ ; Li _(3-f) J ₂ (PO ₄ ) ₃ (0 ≤ f ≤ 2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0 ≤ f ≤ 2); A compound represented by any one of the formulas of LiFePO _{4 may be used:}

In the above formula, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

For example, LiCoO ₂ , LiMn _x O _2x (x=1, 2), LiNi _{1 -x} Mn _x O _2x (0<x<1), LiNi _{1 -x- y} Co _x Mn _y O ₂ (0≤ x≤0.5, 0≤y≤0.5), FePO ₄ and the like.

In the positive active material composition, the conductive material, binder, and solvent may be the same as in the case of the above-described negative active material composition. In some cases, it is also possible to form pores in the electrode plate by further adding a plasticizer to the positive active material composition and the negative active material composition. The content of the positive active material, the conductive material, the binder, and the solvent is a level commonly used in a lithium battery.

The positive electrode current collector has a thickness of 3 μm to 500 μm, and is not particularly limited as long as it has high conductivity without causing a chemical change in the battery. For example, stainless steel, aluminum, nickel, titanium, or sintered carbon , or a surface treated with carbon, nickel, titanium, silver, etc. on the surface of aluminum or stainless steel may be used. The current collector may increase the adhesion of the positive electrode active material by forming fine irregularities on the surface thereof, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam body, and a nonwoven body are possible.

The prepared positive electrode active material composition may be directly coated and dried on a positive electrode current collector to manufacture a positive electrode plate. Alternatively, a positive electrode plate may be manufactured by casting the positive electrode active material composition on a separate support and then laminating a film obtained by peeling from the support on a positive electrode current collector.

The positive electrode and the negative electrode may be separated by a separator, and any separator commonly used in a lithium battery may be used as the separator. In particular, it is suitable that the electrolyte has a low resistance to ion movement and an excellent electrolyte moisture content. For example, as a material selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), and combinations thereof, nonwoven fabric or woven fabric may be used. The separator has a pore diameter of 0.01 to 10 μm and a thickness of generally 5 to 300 μm.

The lithium salt-containing non-aqueous electrolyte consists of a non-aqueous electrolyte and lithium. As the non-aqueous electrolyte, a non-aqueous electrolyte, a solid electrolyte, an inorganic solid electrolyte, and the like are used.

Examples of the non-aqueous electrolyte include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and fluorinated ethylene carbonate. , ethylene methylene carbonate, methyl propyl carbonate, ethyl propanoate, methyl acetate, ethyl acetate, propyl acetate, dimethyl ester gamma-butylolactone, 1,2-dimethoxy ethane, tetrahydrofuran, 2-methyl tetrahydrofuran, Dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, phosphoric acid triester, trimethoxymethane, dioxolane derivative, sulfolane, methyl Aprotic organic solvents such as sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ether, methyl pyropionate, and ethyl propionate can be used.

Examples of the organic solid electrolyte include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphoric acid ester polymers, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, polymers containing ionic dissociation groups, etc. 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, sulfates, etc. of Li such as Li ₄ SiO ₄ -LiI-LiOH, Li ₃ PO ₄ -Li ₂ S-SiS _{2 and the like may be used.}

The lithium salt may be used as long as it is commonly used in lithium batteries, and is a material that is good for dissolving 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) 2 NLi, lithium chloro borate, lower aliphatic carboxylic One or more materials such as lithium bonate, lithium tetraphenyl borate, and imide may be used.

Lithium batteries can be classified into lithium ion batteries, lithium ion polymer batteries and lithium polymer batteries according to the type of separator and electrolyte used, and can be classified into cylindrical, prismatic, coin-type, pouch-type, etc. according to the shape, and the size Depending on the type, it can be divided into a bulk type and a thin film type. In addition, both a lithium primary battery and a lithium secondary battery are possible.

Since the manufacturing method of these batteries is well known in the art, detailed description thereof will be omitted.

1 schematically shows a representative structure of a lithium battery according to an embodiment of the present invention.

Referring to FIG. 1 , the lithium battery 200 includes a positive electrode 130 , a negative electrode 120 , and a separator 140 disposed between the positive electrode 130 and the negative electrode 120 . The above-described positive electrode 130 , negative electrode 120 , and separator 140 are wound or folded and accommodated in the battery container 150 . Then, electrolyte may be injected into the battery container 150 and sealed with the encapsulation member 160 to complete the lithium battery 200 . The battery container 150 may have a cylindrical shape, a square shape, a thin film shape, or the like. The lithium battery may be a lithium ion battery.

The lithium secondary battery has a winding type and a stack type depending on the electrode shape, and may be classified into a cylindrical shape, a prismatic shape, a coin type, and a pouch type according to the type of the exterior material.

The lithium battery may be used not only in a battery used as a power source for a small device, but may also be used as a unit battery of a medium or large device battery module including a plurality of batteries.

Examples of the medium and large device include a power tool; xEV, including Electric Vehicle (EV), Hybrid Electric Vehicle (HEV), and Plug-in Hybrid Electric Vehicle (PHEV); Electric two-wheeled vehicles including E-bikes and E-scooters; Electric golf carts; electric truck; electric commercial vehicle; or systems for power storage; Although these etc. are mentioned, It is not limited to these. In addition, the lithium battery may be used in all other applications requiring high output, high voltage and high temperature driving.

Exemplary embodiments are described in more detail through the following examples and comparative examples. However, the examples are for illustrative purposes only, and the scope of the present invention is not limited thereto.

Example One

(Production of negative active material)

First, Si and Fe were mixed at 85 atomic % and 15 atomic %, respectively, and then put into a vacuum induction melting furnace (Yein Tech., Korea), and dissolved in a vacuum atmosphere to minimize oxidation by the atmosphere. A mother alloy was made.

After pulverizing the master alloy prepared in this way into a large lump, it is put into an injection tube of a melt spinner (Yein Tech., Korea), and is heated by high frequency induction heating in an argon gas atmosphere to melt the master alloy, and By spraying the master alloy on the rotating Cu wheel through a nozzle, the alloy was injected in the form of a ribbon and rapidly solidified.

During grinding the produced alloy ribbon for 20 hours using a ball mill, 2 parts by weight of graphite (manufactured by Aekyung Petrochemical Co., Ltd.) per 100 parts by weight of the produced alloy ribbon was added and further pulverized for 4 hours, whereby carbon was discontinuously coated on the surface A silicon-based alloy powder was obtained.

At this time, the average particle diameter (D50) of the alloy powder was about 2.5 μm, and the average particle diameter of the silicon nanoparticles was 20 nm. In addition, the content of carbon included in the silicon-based alloy powder was 1 part by weight per 100 parts by weight of the sum of Si and Fe, and the content of carbon coated on the surface of the silicon-based alloy powder was 100 parts by weight of the sum of Si and Fe It was 1 part by weight per.

(Manufacture of lithium secondary battery)

(Production of cathode)

The negative active material prepared in Example 1, polyimide (PI) as a binder, and carbon conductive material (denka black) as a conductive material were mixed in a weight ratio of 80:10:10, and a solvent N-methylpi was used to adjust the viscosity. Rollidone was added so that the solid content was 60% by weight, thereby preparing a negative active material composition.

The negative active material composition was applied to a thickness of about 40 μm using a conventional method on a copper current collector having a thickness of 15 μm. After drying the current collector coated with the composition at room temperature, drying again at 120° C., rolling and punching to prepare a negative electrode to be applied to a cell of 18650 standard.

(Manufacture of anode)

_{LiNi 1 /3} Co _{1 /3} Mn _{1 /3} O ₂ as a positive electrode active material, polyvinylidene fluoride (PVDF) as a binder, and a carbon conductive material (Denka Black) as a conductive material are mixed in a weight ratio of 90:5:5 and N-methylpyrrolidone solvent was added to adjust the viscosity so that the solid content was 60% by weight to prepare a cathode active material composition

The positive active material composition was applied to a thickness of about 40 μm using a conventional method on an aluminum current collector having a thickness of 15 μm. After drying the current collector coated with the composition at room temperature, drying at 120° C. again, rolling and punching to prepare a positive electrode to be applied to an 18650 standard cell.

(Manufacture of lithium secondary battery-full cell)

The prepared negative electrode, the positive electrode, and a polypropylene separator having a thickness of 14 μm was interposed between the positive electrode and the negative electrode, and an electrolyte was injected and compressed to prepare an 18650 standard cell. At this time, the electrolyte is a mixed solvent of ethylene carbonate (EC), diethyl carbonate (DEC) and fluoroethylene carbonate (FEC) (EC:DEC:FEC is a volume ratio of 5:70:25) with LiPF ₆ of 1.10M What was dissolved so as to become a density|concentration was used.

Example 2

An alloy powder was obtained in the same manner as in Example 1, except that the graphite addition amount was changed to 3 parts by weight per 100 parts by weight of the resulting alloy ribbon. At this time, the average particle diameter (D50) of the alloy powder was about 2.5 μm, and the average particle diameter of the silicon nanoparticles was about 20 nm. In addition, the content of carbon included in the silicon-based alloy powder was 1 part by weight per 100 parts by weight of the sum of Si and Fe, and the content of carbon coated on the surface of the silicon-based alloy powder was 100 parts by weight of the sum of Si and Fe It was 2 parts by weight per sugar.

Thereafter, a lithium secondary battery was manufactured in the same manner as in Example 1, except that the alloy powder was used as an anode active material instead of the alloy powder prepared in Example 1.

Example 3

An alloy powder was obtained in the same manner as in Example 1, except that the graphite addition amount was changed to 4 parts by weight per 100 parts by weight of the resulting alloy ribbon. At this time, the average particle diameter (D50) of the alloy powder was about 2.5 μm, and the average particle diameter of the silicon nanoparticles was about 20 nm. In addition, the content of carbon included in the silicon-based alloy powder was 1 part by weight per 100 parts by weight of the sum of Si and Fe, and the content of carbon coated on the surface of the silicon-based alloy powder was 100 parts by weight of the sum of Si and Fe It was 3 parts by weight per sugar.

Thereafter, a lithium secondary battery was manufactured in the same manner as in Example 1, except that the alloy powder was used as an anode active material instead of the alloy powder prepared in Example 1.

Example 4

An alloy powder was obtained in the same manner as in Example 1, except that the graphite addition amount was changed to 5 parts by weight per 100 parts by weight of the resulting alloy ribbon. At this time, the average particle diameter (D50) of the alloy powder was about 2.5 μm, and the average particle diameter of the silicon nanoparticles was about 20 nm. In addition, the content of carbon included in the silicon-based alloy powder was 1 part by weight per 100 parts by weight of the sum of Si and Fe, and the content of carbon coated on the surface of the silicon-based alloy powder was 100 parts by weight of the sum of Si and Fe It was 4 parts by weight per sugar.

Thereafter, a lithium secondary battery was manufactured in the same manner as in Example 1, except that the alloy powder was used as an anode active material instead of the alloy powder prepared in Example 1.

Example 5

An alloy powder was obtained in the same manner as in Example 1, except that the graphite addition amount was changed to 6 parts by weight per 100 parts by weight of the resulting alloy ribbon. At this time, the average particle diameter (D50) of the alloy powder was about 2.5 μm, and the average particle diameter of the silicon nanoparticles was about 20 nm. In addition, the content of carbon contained in the silicon-based alloy powder was 2 parts by weight per 100 parts by weight of the sum of Si and Fe, and the content of carbon coated on the surface of the silicon-based alloy powder was 100 parts by weight of the sum of Si and Fe It was 4 parts by weight per sugar.

Thereafter, a lithium secondary battery was manufactured in the same manner as in Example 1, except that the alloy powder was used as an anode active material instead of the alloy powder prepared in Example 1.

Example 6

An alloy powder was obtained in the same manner as in Example 1, except that the graphite addition amount was changed to 9 parts by weight per 100 parts by weight of the resulting alloy ribbon. At this time, the average particle diameter (D50) of the alloy powder was about 2.5 μm, and the average particle diameter of the silicon nanoparticles was about 20 nm. In addition, the content of carbon included in the silicon-based alloy powder was 3 parts by weight per 100 parts by weight of the sum of Si and Fe, and the content of carbon coated on the surface of the silicon-based alloy powder was 100 parts by weight of the sum of Si and Fe It was 6 parts by weight per sugar.

Thereafter, a lithium secondary battery was manufactured in the same manner as in Example 1, except that the alloy powder was used as an anode active material instead of the alloy powder prepared in Example 1.

Example 7

An alloy powder was obtained in the same manner as in Example 1, except that the graphite addition amount was changed to 10 parts by weight per 100 parts by weight of the resulting alloy ribbon. At this time, the average particle diameter (D50) of the alloy powder was about 2.5 μm, and the average particle diameter of the silicon nanoparticles was about 20 nm. In addition, the content of carbon included in the silicon-based alloy powder was 4 parts by weight per 100 parts by weight of the sum of Si and Fe, and the content of carbon coated on the surface of the silicon-based alloy powder was 100 parts by weight of the sum of Si and Fe It was 6 parts by weight per sugar.

Thereafter, a lithium secondary battery was manufactured in the same manner as in Example 1, except that the alloy powder was used as an anode active material instead of the alloy powder prepared in Example 1.

Example 8

While the alloy ribbon prepared in Example 1 was pulverized for 14 hours using a ball mill, 5 parts by weight of graphite per 100 parts by weight of the resulting alloy ribbon was added and further pulverized for 10 hours, whereby carbon was discontinuously coated on the surface A silicon-based alloy powder was obtained.

At this time, the average particle diameter (D50) of the alloy powder was about 2.5 μm, and the average particle diameter of the silicon nanoparticles was 20 nm. In addition, the content of carbon contained in the silicon-based alloy powder was 2 parts by weight per 100 parts by weight of the sum of Si and Fe, and the content of carbon coated on the surface of the silicon-based alloy powder was 100 parts by weight of the sum of Si and Fe 3 parts by weight per

Thereafter, a lithium secondary battery was manufactured in the same manner as in Example 4, except that the alloy powder was used as an anode active material instead of the alloy powder prepared in Example 4.

Example 9

While the alloy ribbon prepared in Example 1 was pulverized for 8 hours using a ball mill, 5 parts by weight of graphite per 100 parts by weight of the resulting alloy ribbon was added and further pulverized for 16 hours, whereby carbon was discontinuously coated on the surface A silicon-based alloy powder was obtained.

At this time, the average particle diameter (D50) of the alloy powder was about 2.5 μm, and the average particle diameter of the silicon nanoparticles was 20 nm. In addition, the content of carbon included in the silicon-based alloy powder was 3 parts by weight per 100 parts by weight of the sum of Si and Fe, and the content of carbon coated on the surface of the silicon-based alloy powder was 100 parts by weight of the sum of Si and Fe 2 parts by weight per

Thereafter, a lithium secondary battery was manufactured in the same manner as in Example 4, except that the alloy powder was used as an anode active material instead of the alloy powder prepared in Example 4.

Example 10

In the same manner as in Example 1, except that boric acid (manufactured by Aldrich) was added so that 2 parts by weight of boron per 100 parts by weight of the resulting alloy ribbon was added instead of graphite, boron was discontinuously formed on the surface of the silicon-based alloy powder. An alloy powder was obtained. At this time, the average particle diameter (D50) of the alloy powder was about 2.5 μm, and the average particle diameter of the silicon nanoparticles was 20 nm. In addition, the content of boron contained in the silicon-based alloy powder was 1 part by weight per 100 parts by weight of the sum of Si and Fe, and the content of boron coated on the surface of the silicon-based alloy powder was 100 parts by weight of the sum of Si and Fe 1 part by weight per

Thereafter, a lithium secondary battery was manufactured in the same manner as in Example 1, except that the alloy powder was used as an anode active material instead of the alloy powder prepared in Example 1.

Example 11

In the same manner as in Example 1, except that boric acid (manufactured by Aldrich) was added so that 6 parts by weight of boron per 100 parts by weight of the resulting alloy ribbon was added instead of graphite, boron was discontinuously formed on the surface of the silicon-based alloy powder. An alloy powder was obtained. At this time, the average particle diameter (D50) of the alloy powder was about 2.5 μm, and the average particle diameter of the silicon nanoparticles was 20 nm. In addition, the content of boron contained in the silicon-based alloy powder was 2 parts by weight per 100 parts by weight of the sum of Si and Fe, and the content of boron coated on the surface of the silicon-based alloy powder was 100 parts by weight of the sum of Si and Fe was 4 parts by weight per

Thereafter, a lithium secondary battery was manufactured in the same manner as in Example 1, except that the alloy powder was used as an anode active material instead of the alloy powder prepared in Example 1.

Example 12

In the same manner as in Example 1, except that boric acid (manufactured by Aldrich) was added so that 9 parts by weight of boron per 100 parts by weight of the resulting alloy ribbon was added instead of graphite, boron was discontinuously formed on the surface of the silicon-based alloy powder. An alloy powder was obtained. At this time, the average particle diameter (D50) of the alloy powder was about 2.5 μm, and the average particle diameter of the silicon nanoparticles was 20 nm. In addition, the content of boron contained in the silicon-based alloy powder was 3 parts by weight per 100 parts by weight of the sum of Si and Fe, and the content of boron coated on the surface of the silicon-based alloy powder was 100 parts by weight of the sum of Si and Fe 6 parts by weight per

Thereafter, a lithium secondary battery was manufactured in the same manner as in Example 1, except that the alloy powder was used as an anode active material instead of the alloy powder prepared in Example 1.

Example 13

In the same manner as in Example 1, except that boric acid (manufactured by Aldrich) was added so that 10 parts by weight of boron per 100 parts by weight of the resulting alloy ribbon was added instead of graphite, boron was discontinuously formed on the surface of the silicon-based alloy powder. An alloy powder was obtained. At this time, the average particle diameter (D50) of the alloy powder was about 2.5 μm, and the average particle diameter of the silicon nanoparticles was 20 nm. In addition, the content of boron contained in the silicon-based alloy powder was 4 parts by weight per 100 parts by weight of the sum of Si and Fe, and the content of boron coated on the surface of the silicon-based alloy powder was 100 parts by weight of the sum of Si and Fe 6 parts by weight per

Thereafter, a lithium secondary battery was manufactured in the same manner as in Example 1, except that the alloy powder was used as an anode active material instead of the alloy powder prepared in Example 1.

Example 14

_{An alloy powder was obtained in the same manner as in Example 6, except that 2 parts by weight of iron oxide Fe 2} O ₃ (manufactured by Aldrich) was further added per 100 parts by weight of the sum of Si and Fe in the master alloy manufacturing step. .

At this time, the average particle diameter (D50) of the alloy powder was about 2.5 μm, and the average particle diameter of the silicon nanoparticles was about 20 nm. In addition, the content of carbon contained in the silicon-based alloy powder was 3 parts by weight per 100 parts by weight of the sum of Si and Fe, and the content of carbon coated on the surface of the silicon-based alloy powder was 100 parts by weight of the sum of Si and Fe It was 6 parts by weight per sugar.

Thereafter, a lithium secondary battery was manufactured in the same manner as in Example 6, except that the alloy powder was used as an anode active material instead of the alloy powder prepared in Example 6.

Example 15

_{An alloy powder was obtained in the same manner as in Example 6, except that 4 parts by weight of iron oxide Fe 2} O ₃ (manufactured by Aldrich) was further added per 100 parts by weight of the Si and Fe in the master alloy manufacturing step. .

At this time, the average particle diameter (D50) of the alloy powder was about 2.5 μm, and the average particle diameter of the silicon nanoparticles was about 20 nm. In addition, the content of carbon contained in the silicon-based alloy powder was 3 parts by weight per 100 parts by weight of the sum of Si and Fe, and the content of carbon coated on the surface of the silicon-based alloy powder was 100 parts by weight of the sum of Si and Fe It was 6 parts by weight per sugar.

Thereafter, a lithium secondary battery was manufactured in the same manner as in Example 6, except that the alloy powder was used as an anode active material instead of the alloy powder prepared in Example 6.

Example 16

_{An alloy powder was obtained in the same manner as in Example 6, except that 6 parts by weight of iron oxide Fe 2} O ₃ (manufactured by Aldrich) was further added per 100 parts by weight of the Si and Fe in the master alloy manufacturing step. .

At this time, the average particle diameter (D50) of the alloy powder was about 2.5 μm, and the average particle diameter of the silicon nanoparticles was about 20 nm. In addition, the content of carbon contained in the silicon-based alloy powder was 3 parts by weight per 100 parts by weight of the sum of Si and Fe, and the content of carbon coated on the surface of the silicon-based alloy powder was 100 parts by weight of the sum of Si and Fe It was 6 parts by weight per sugar.

Thereafter, a lithium secondary battery was manufactured in the same manner as in Example 6, except that the alloy powder was used as an anode active material instead of the alloy powder prepared in Example 6.

comparative example 1 (absence of additive element (A))

A silicon-based alloy powder was obtained in the same manner as in Example 1, except that graphite was not added. At this time, the average particle diameter (D50) of the silicon-based alloy powder was about 2.4 μm, and the average particle diameter of the silicon nanoparticles was 20 nm.

Thereafter, a lithium secondary battery was manufactured in the same manner as in Example 1, except that the alloy powder was used as an anode active material instead of the alloy powder prepared in Example 1.

comparative example 2 (alloy powder on the surface Absence of additive element (A))

By using the same method as in Example 1 except that 5 parts by weight of graphite per 100 parts by weight of the sum of the weights of Si and Fe was added at the same time as Si and Fe during the preparation of the master alloy, and graphite was not added thereafter, by using the same method as in Example 1, carbon only inside was added, and a silicon-based alloy powder with no carbon coating on the surface was obtained. At this time, the average particle diameter (D50) of the alloy powder was about 2.7 μm, and the average particle diameter of the silicon nanoparticles was 25 nm. In addition, the content of carbon included in the silicon-based alloy powder was 5 parts by weight per 100 parts by weight of the sum of Si and Fe.

Thereafter, a lithium secondary battery was manufactured in the same manner as in Example 1, except that the alloy powder was used as an anode active material instead of the alloy powder prepared in Example 1.

comparative example 3 (absence of additive element (A) inside alloy powder)

Instead of adding graphite during pulverization of the produced alloy ribbon, 5 parts by weight of graphite per 100 parts by weight of pulverized alloy ribbon was added and blended after pulverization was completed. By using the same method as in Example 1, A silicon-based alloy powder in which carbon was not added and carbon was discontinuously coated only on the surface was obtained. At this time, the average particle diameter (D50) of the alloy powder was about 3.0 μm, and the average particle diameter of the silicon nanoparticles was 26 nm. In addition, the content of carbon coated on the surface of the silicon-based alloy powder was 5 parts by weight per 100 parts by weight of the sum of Si and Fe.

Thereafter, a lithium secondary battery was manufactured in the same manner as in Example 1, except that the alloy powder was used as an anode active material instead of the alloy powder prepared in Example 1.

(Analysis of negative electrode active material)

evaluation example 1: of the negative active material porosity measurement

The porosity inside the alloy powders prepared in Examples 1 to 16 and Comparative Examples 1 to 3 was measured as follows.

First, in order to obtain the density of the alloy powder measured at a pressure of 20 kN, 5 g of the alloy powder was placed in a conductivity measuring equipment MCP-PD51 (manufactured by Mitsubishi Chemical), and then it was rolled at a pressure of 20 kN. was measured, and the measurement was repeated 5 times, and the average value was taken as the density value of the alloy powder. At this time, the measurement was made at 25 ℃.

Next, in order to obtain the true density of the alloy powder, 5 g of the alloy powder was prepared and then the true density was measured using a gas pycnometer TM1330 (manufactured by Micromeritics AccuPycTM) using helium gas as an inert gas, and the measurement was performed using 5 g of the alloy powder. It was repeated several times and the average value was taken as the true density value of the alloy powder. At this time, the measurement was made at 25 ℃.

Next, the porosity inside the alloy powder was measured according to Equation 1, and is shown in Tables 1 and 2 below.

Furtherance
ratio
(atom%) C or B's
Total content*
(parts by weight) O's
Total content*
(parts by weight) alloy powder
undergarment
C or B's
content*
(parts by weight) alloy powder
surface
top
C or B's
content*
(parts by weight) alloy
powder
undergarment
O's
content*
(parts by weight) alloy powder
true density
(g/cc)
alloy powder
density
(g/cc,
@20 kN) alloy powder
internal
porosity
(%) Si Fe C B C B C B Example 1 85 15 2 - - One - One - - 3.50 2.28 34.96 Example 2 85 15 3 - - One - 2 - - 3.69 2.40 34.89 Example 3 85 15 4 - - One - 3 - - 3.63 2.47 32.01 Example 4 85 15 5 - - One - 4 - - 3.60 2.46 31.72 Example 5 85 15 6 - - 2 - 4 - - 3.50 2.52 27.96 Example 6 85 15 9 - - 3 - 6 - - 3.58 2.59 27.65 Example 7 85 15 10 - - 4 - 6 - - 3.53 2.61 26.06 Example 8 85 15 5 - - 2 - 3 - - 3.62 2.50 30.99 Example 9 85 15 5 - - 3 - 2 - - 3.63 2.51 30.83 Example 10 85 15 - 2 - - One - One - 3.53 2.30 34.92 Example 11 85 15 - 6 - - 2 - 4 - 3.51 2.37 32.67 Example 12 85 15 - 9 - - 3 - 6 - 3.59 2.42 32.59 Example 13 85 15 - 10 - - 4 - 6 - 3.56 2.44 31.38 Example 14 85 15 9 - 2 3 - 6 - 2 3.61 2.65 26.59 Example 15 85 15 9 - 4 3 - 6 - 4 3.59 2.69 25.07 Example 16 85 15 9 - 6 3 - 6 - 6 3.62 2.75 24.03 Comparative Example 1 85 15 - - - - - - 3.52 2.23 36.80 Comparative Example 2 85 15 5 - 5 - - - 3.51 2.17 38.10 Comparative Example 3 85 15 5 - - 5 - - 3.59 2.13 40.50

(* The total content of C or B, the total content of O, the content of C or B in the alloy powder, the content of C or B on the surface of the alloy powder, and the content of O in the alloy powder are the Si and Fe Measured based on 100 parts by weight in total.)

As shown in Table 1 and Figure 2, in the case of the alloy powder of Examples 1 to 13 in which carbon or boron is present in the silicon-based alloy powder, the alloy of Comparative Example 1 in which carbon is not present in the silicon-based alloy powder It can be seen that the porosity inside the alloy powder is lower than that of the powder and the alloy powder of Comparative Example 3. In addition, the internal porosity of the alloy powder of Comparative Example 2, in which carbon exists only inside the silicon-based alloy powder, showed 35% or more, which only serves as a matrix by carbon forming an alloy with Si and/or Fe. It means that it could not contribute to the reduction.

In addition, as the amount of carbon or boron inside the silicon-based alloy powder increases, it can be seen that the porosity inside the alloy powder is reduced. Therefore, by controlling the amount of carbon or boron inside the silicon-based alloy powder, it can be confirmed that the porosity inside the alloy powder can be adjusted.

In addition, it can be seen that when an oxygen atom is additionally included in the silicon-based alloy powder, that is, Examples 14 to 16 have lower porosity in the alloy powder as compared to Example 6. Thus, it was confirmed that the density of the powder was lowered by the compound containing oxygen atoms.

evaluation example 2: Analysis of the surface and cross-section of the negative active material

In order to confirm the shape of the alloy powder, a scanning electron microscope analysis of the alloy powder prepared in Example 1 was performed at 1000 magnification, and the results are shown in the left drawing of FIG. 3 .

As shown in the left drawing of FIG. 3 , it can be seen that island-type carbon is discontinuously coated on the surface of the alloy powder.

Next, in order to confirm the internal porosity of the alloy powder, the cross-sections of the alloy powders prepared in Examples 1, 3 to 6, and Comparative Example 1 were analyzed using SEM. Specifically, the SEM measurement was made at 3000 magnification, and the results are shown in FIGS. 3 to 7 .

In the case of the alloy powders prepared in Examples 1 and 3 to 6 (see FIGS. 3 to 6 ) in which carbon or boron is present in the silicon-based alloy powder, Comparative Example 1 in which carbon is not present in the silicon-based alloy powder Compared to the alloy powder (see FIG. 7), it can be seen that the voids inside the powder are significantly reduced. In addition, it can be seen that as the amount of carbon inside the silicon-based alloy powder increases, the voids inside the powder decrease, which is consistent with the trend of the porosity measured in Evaluation Example 1.

evaluation example 3: Analysis of internal components of negative active material

In order to analyze the components inside the alloy powder of the alloy powder prepared in Example 1, TEM analysis (130,000 magnification) was performed, and the results are shown in FIG. 8 . For component-specific analysis, only the brightness of some of 8(a) was shown by changing ( FIGS. 8(b), 8(c) and 8(d)). The bright part in 8(b) represents Si particles, the bright part in 8(d) represents carbon, and the gray part excluding Si and carbon in 8(c) represents a compound composed of Si and Fe. As shown in FIG. 8( a ), Si particles (shown in gray) are dispersed in a matrix made of the compounds (shown in black) made of Si and Fe, and amorphous carbon (shown in white) is dispersed in the matrix. mark) was located. Therefore, it can be confirmed that the voids inside the alloy powder are reduced by the carbon.

In addition, in order to analyze the components inside the alloy powder prepared in Example 14, HAADF-STEM analysis and energy dispersive X-ray (EDX) analysis of oxygen atoms were performed, and as a result, is shown in FIG. 9 . As shown in the left photo of FIG. 9 , it can be seen that Si particles (shown in black) are dispersed in the matrix made of the compounds (shown in gray) made of Si and Fe, and the oxygen atom EDX for this photo As a result of the analysis, it can be seen that the oxygen atoms (shown in green) are evenly dispersed and located at the interface between the Si particles and the compounds composed of Si and Fe (see the right photo of FIG. 9 ).

At this time, in order to analyze the component of the oxygen atom-containing compound, HAADF-STEM analysis (350,000 magnification) was performed again on some of the parts indicated in green in the right photograph of FIG. 9 , and is shown in FIG. 10 . Thereafter, EDX analysis was performed on the solid line portion of FIG. 10 , and is shown in FIG. 11 .

As shown in FIG. 11 , the intensity of O is increased in portions A to B of FIG. 10 , while the contents of Si and Fe are decreasing, so it can be seen that portions A to B are oxygen atom-containing compounds. At this time, from a thermodynamic point of view considering Gibbs' free energy, since the affinity between Si and O is greater than that between Fe and O, it is predicted that the oxygen atom will first combine with Si to form a stable compound. Specifically, -ΔG ⁰ ₂₉₈ of _{SiO 2} (25° C.) is 805067 J/mol, whereas -ΔG ⁰ ₂₉₈ of _{Fe 2} O ₃ (25° C.) is 744224 J/mol, so it can be seen that _{the oxygen atom-containing compound produced according to the above embodiment mainly includes SiO 2} and some Fe ₂ O _{3 .}

evaluation example 4: Component analysis of the inside and surface of the negative active material

In order to analyze the existence form of carbon inside and the existence form of carbon outside of the alloy powders prepared in Examples 4, 8 and 9, X-ray photoelectron spectroscopy (XPS) was performed and the result is shown in FIG. 12 .

In the XPS graph, a peak appearing at about 283 eV to about 285 eV means that there is a C-C bond in the test sample, and a peak appearing at about 282 eV to 283 eV means that a Si-C bond exists in the test sample. As shown in FIG. 12, even if the total content of carbon contained in the alloy powder is the same, the higher the content of carbon coated on the surface of the silicon-based alloy powder, the more CC bonds (Example 4), and the inside of the silicon-based alloy powder It can be seen that the higher the carbon content, the more Si-C bonds (Example 9). This is believed to be because carbon in the alloy powder combines with Si to form a SiC compound.

evaluation example 5: of lithium battery charging and discharging Afterwards, internal analysis of the anode active material

After charging and discharging, in order to check the change of the carbon material inside the alloy powder, the lithium secondary battery prepared in Example 1 was charged with a current of 1.0C at 25°C with a charging voltage of 4.2V (vs. Li). cutoff voltage) in a constant current mode (constant current mode: CC mode), and while maintaining a voltage of 4.2V, it was charged in a constant voltage mode (constant voltage mode: CV mode) until the current reached a rate of 0.01C. Then, it was discharged in the constant current mode of 0.2C until the discharge termination voltage of 2.5V. Thereafter, the charging/discharging cycle was repeated up to 100 times in the same current and voltage section, and TEM analysis of the alloy powder of the alloy powder charged and discharged 100 times was performed, and the results are shown in FIG. 13 .

The material in the dotted ellipse of FIG. 13 means carbon, and as shown in FIG. 13 , it can be seen that the carbon atoms in the alloy powder exist in a similar form even after 100 times of charging and discharging of the lithium battery. This means that the generation of side reactants that may be generated by the electrolyte is suppressed by the carbon atoms filled in the pores inside the alloy powder.

evaluation example 6: Evaluation of Lithium Battery Lifetime Characteristics

After charging and discharging the lithium secondary batteries prepared in Examples 1 to 17 and Comparative Examples 1 to 3 according to the method of Evaluation Example 5, the charge/discharge cycle is repeated up to 100 times in the same current and voltage section Thus, capacity retention rate (CRR) was measured. The results are shown in Table 2, Figure 2, Figure 14 and Figure 15, wherein the capacity retention rate is defined by the following Equation 2:

<Equation 2>

Capacity retention ratio [%] = [discharge capacity in each cycle/1 discharge capacity in ^st cycle] x 100

Furtherance
ratio
(atom%) Total content of C or B*
(parts by weight) O's
Total content*
(parts by weight) alloy
powder
undergarment
Content of C or B*
(parts by weight) alloy powder
surface
top
C or B's
content*
(parts by weight) alloy
powder
undergarment
O's
content*
(parts by weight) alloy powder
internal
Porosity (%) CRR
(%) Si Fe C B C B C B Example 1 85 15 2 - - One - One - - 34.96 72 Example 2 85 15 3 - - One - 2 - - 34.89 78 Example 3 85 15 4 - - One - 3 - - 32.01 83 Example 4 85 15 5 - - One - 4 - - 31.72 86 Example 5 85 15 6 - - 2 - 4 - - 27.96 94 Example 6 85 15 9 - - 3 - 6 - - 27.65 95 Example 7 85 15 10 - - 4 - 6 - - 26.06 80 Example 8 85 15 5 - - 2 - 3 - - 30.99 82.2 Example 9 85 15 5 - - 3 - 2 - - 30.83 78.6 Example 10 85 15 - 2 - - One - One - 34.92 72 Example 11 85 15 - 6 - - 2 - 4 - 32.67 82 Example 12 85 15 - 9 - - 3 - 6 - 32.59 71 Example 13 85 15 - 10 - - 4 - 6 - 31.38 70 Example 14 85 15 9 - 2 3 - 6 - 2 26.59 95 Example 15 85 15 9 - 4 3 - 6 - 4 25.07 96 Example 16 85 15 9 - 6 3 - 6 - 6 24.03 97 Comparative Example 1 85 15 - - - - - - - 36.80 69 Comparative Example 2 85 15 5 - 5 - - - - 38.10 61 Comparative Example 3 85 15 5 - - - 5 - - 40.50 55

(* The total content of C or B, the total content of O, the content of C or B in the alloy powder, the content of C or B on the surface of the alloy powder, and the content of O in the alloy powder are the Si and Fe Measured based on 100 parts by weight in total.)

As shown in Table 2, FIGS. 14 and 15, in the case of the alloy powders prepared in Examples 1 to 13 in which carbon or boron is present in the silicon-based alloy powder, carbon or boron in both the interior and the surface of the silicon-based alloy powder As compared to the alloy powder or alloy powder of Comparative Examples 1 to 3 in which is does not exist, it can be seen that the life characteristics are remarkably improved. In addition, as the amount of carbon or boron in the silicon-based alloy powder increases, the lifetime characteristics of the lithium battery tend to improve, which is consistent with the trend of the porosity measured in Evaluation Example 1.

In addition, as shown in FIG. 2 , it can be seen that the lifetime characteristics are further improved at a certain amount of carbon or boron in the silicon-based alloy powder. It is believed that this is because it serves as a buffer for the expansion of Si.

In addition, even if the content of carbon contained in the alloy powder is the same (Examples 4, 8 and 9), it can be seen that the higher the carbon content on the surface of the silicon-based alloy powder, the better the lifespan characteristics. This is considered to be due to the increase of the electrical conductivity of the negative electrode by carbon on the surface of the powder together with the decrease of the internal voids.

In addition, when an oxygen atom is additionally included in the silicon-based alloy powder, that is, Examples 14 to 16 exhibited a lower porosity and a capacity retention rate equal to or greater than that of Example 6. Accordingly, it can be seen that by additionally including an oxygen atom in the silicon-based alloy powder, the lifespan characteristics of a lithium battery employing an anode including the same can be improved.

In the above, the preferred embodiments according to the present invention have been described with reference to the drawings and examples, but these are merely exemplary, and various modifications and equivalent other embodiments are possible by those skilled in the art. will be able to understand Accordingly, the protection scope of the present invention should be defined by the appended claims.

120: negative electrode 130: positive electrode
140: separator 150: battery container
160: encapsulation member 200: lithium battery

Claims (23)

As an anode active material comprising a silicon-based alloy powder,
The silicon-based alloy powder,
silicon (Si); a first metal (M ₁ ); and an additive element (A);
The first metal (M ₁ ) is titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga) and germanium (Ge),
The additive element (A) is one or more selected from carbon (C), boron (B), sodium (Na), nitrogen (N), phosphorus (P), sulfur (S) and chlorine (Cl),
The additive element (A) is disposed on the inside and the surface of the silicon-based alloy powder,
The porosity inside the silicon-based alloy powder is 20% to 35%, wherein the porosity is an anode active material represented by the following Equation 1:
<Equation 1>

. According to claim 1,
The silicon-based alloy powder,
a matrix including the silicon and the first metal (M _{1 );}
silicon nanoparticles dispersed in the matrix; and
An anode active material having a structure including; the additive element (A) disposed in the matrix and on the surface of the silicon-based alloy powder. 3. The method of claim 2,
The matrix includes a compound phase consisting of the silicon and the first metal (M ₁ ), and the silicon nanoparticles include a single phase of the silicon. 3. The method of claim 2,
An anode active material in which at least a portion of the additive element (A) disposed in the matrix is present in the form of silicide. According to claim 1,
An anode active material wherein the first metal (M ₁ ) is iron (Fe). According to claim 1,
The silicon-based alloy powder is represented by _{Si-M 1 -A,}
In the silicon-based alloy powder,
Based on the silicon and the _{total number of atoms of the first metal (M 1} ), the content of Si is 50 atomic% to 90 atomic%, and the _{content of the first metal (M 1} ) is 10 atomic% to 50 atoms %ego,
Based on 100 parts by weight of the sum of the silicon and the first metal (M ₁ ), the total content of the additive element (A) is 0.01 parts by weight to 20 parts by weight,
The total content of the additive element (A) is a negative active material that is the sum of the content of the additive element (A) disposed inside the silicon-based alloy powder and the content of the additive element (A) disposed on the surface. According to claim 1,
The anode active material wherein the silicon-based alloy powder further comprises an oxygen (O) atom. 8. The method of claim 7,
The silicon-based alloy powder,
a matrix comprising the silicon, the first metal (M ₁ ) and oxygen (O) atoms;
silicon nanoparticles dispersed in the matrix; and
An anode active material having a structure comprising; the additive element (A) disposed in the matrix and on the surface of the silicon-based alloy powder. 9. The method of claim 8,
The matrix includes a compound phase consisting of the silicon and the first metal (M ₁ ) and a compound phase consisting of the silicon and the oxygen (O) atom, and the silicon nanoparticles include a single phase of the silicon. . 10. The method of claim 9,
The matrix further comprises a compound phase consisting of the first metal (M ₁ ) and the oxygen (O) atoms. 8. The method of claim 7,
The silicon-based alloy powder is represented by _{Si-M 1 -AO,}
In the silicon-based alloy powder,
Based on the silicon and the _{total number of atoms of the first metal (M 1} ), the content of Si is 50 atomic% to 90 atomic%, and the _{content of the first metal (M 1} ) is 10 atomic% to 50 atomic% ego,
Based on 100 parts by weight of the sum of the silicon and the first metal (M ₁ ), the total content of the additive element (A) is 0.01 parts by weight to 20 parts by weight, and the content of the oxygen (O) atom is 0.01 parts by weight to 50 parts by weight of the negative electrode active material. 8. The method of claim 7,
The silicon-based alloy powder is represented by _{Si-M 1 -CBO,}
In the silicon-based alloy powder,
Based on the silicon and the _{total number of atoms of the first metal (M 1} ), the content of Si is 50 atomic% to 90 atomic%, and the _{content of the first metal (M 1} ) is 10 atomic% to 50 atomic% ego,
Based on 100 parts by weight of the sum of the silicon and the first metal (M ₁ ), the total content of C is 0.01 parts by weight to 20 parts by weight, and the total content of B is 0 parts by weight to 20 parts by weight, The negative active material having an O content of 0.01 parts by weight to 50 parts by weight. According to claim 1,
The silicon-based powder alloy further comprises a second metal (M ₂ ),
The second metal (M ₂ ) is manganese (Mn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), silver (Ag), tin (Sn), tantalum (Ta), and tungsten (W) an anode active material selected from among. 14. The method of claim 13,
The silicon-based alloy powder is represented by Si-M ₁ -M ₂ -A,
The second metal (M ₂ ) is manganese (Mn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), silver (Ag), tin (Sn), tantalum (Ta), and tungsten (W) is selected from;
In the silicon-based alloy powder,
Based on the total number of atoms of the silicon, the first metal (M ₁ ), and the second metal (M ₂ ), the content of Si is 50 to 90 atomic%, the first metal (M ₁ ) The content is 10 atomic% to 50 atomic%, the _{content of the second metal (M 2} ) is more than 0 atomic% to 10 atomic%,
Based on 100 parts by weight of the sum of the silicon, the first metal (M ₁ ) and the second metal (M ₂ ), the total content of the additive element (A) is 0.01 parts by weight to 20 parts by weight,
The total content of the additive element (A) is a negative active material that is the sum of the content of the additive element (A) disposed inside the silicon-based alloy powder and the content of the additive element (A) disposed on the surface. 15. The method of claim 14,
Based on 100 parts by weight of the sum of the silicon, the first metal (M ₁ ), and the second metal (M ₂ ), the total content of the additive element (A) is 1 part by weight to 9 parts by weight of the negative active material. 15. The method of claim 14,
An anode active material in which the content of the additive element (A) disposed on the surface of the silicon-based alloy powder is equal to or greater than the content of the additive element (A) contained in the silicon-based alloy powder. 15. The method of claim 14,
The content of the additive element (A) disposed in the silicon-based alloy powder is 0.1 parts by weight to 4 parts by weight based on 100 parts by weight of the sum _{of the silicon, the first metal (M 1} ) and the second metal (M _{2 )} wealth;
The content of the additive element (A) disposed on the surface of the silicon-based alloy powder is 0.5 parts by weight to 7 parts by weight based on 100 parts by weight of the sum _{of the silicon, the first metal (M 1} ), and the second metal (M _{2 )} negative active material in parts by weight. According to claim 1,
The silicon-based powder alloy further comprises a second metal (M ₂ ),
The silicon-based alloy powder further comprises an oxygen (O) atom,
The silicon-based alloy powder is represented by Si-M ₁ -M ₂ -AO,
The second metal (M ₂ ) is manganese (Mn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), silver (Ag), tin (Sn), tantalum (Ta), and tungsten (W) is selected from;
In the silicon-based alloy powder,
Based on the total number of atoms of the silicon, the first metal (M ₁ ) and the second metal (M ₂ ), the content of Si is 50 to 90 atomic%, and the content of _{the first metal (M 1 )} This 10 atomic % to 50 atomic %, the _{content of the second metal (M 2} ) is more than 0 atomic % to 10 atomic %,
Based on 100 parts by weight of the sum of the silicon, the first metal (M ₁ ) and the second metal (M ₂ ), the total content of the additive element (A) is 0.01 parts by weight to 20 parts by weight, and the oxygen (O ) an anode active material having an atom content of 0.01 parts by weight to 50 parts by weight. 19. The method of claim 18,
The silicon-based alloy powder,
a matrix comprising the silicon, the first metal (M ₁ ), the second metal (M ₂ ), and oxygen (O) atoms;
silicon nanoparticles dispersed in the matrix; and
has a structure comprising; the additive element (A) disposed in the matrix and on the surface of the silicon-based alloy powder,
The matrix includes a compound phase consisting of the silicon and the first metal (M ₁ ), a compound phase consisting of the silicon and the second metal (M ₂ ), and a compound phase consisting of the silicon and the oxygen (O) atoms do,
The negative active material wherein the silicon nanoparticles include a single phase of the silicon. According to claim 1,
The silicon-based powder alloy further comprises a second metal (M ₂ ),
The silicon-based alloy powder further comprises an oxygen (O) atom,
The silicon-based alloy powder is represented by Si-M ₁ -M ₂ -CBO,
The second metal (M ₂ ) is manganese (Mn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), silver (Ag), tin (Sn), tantalum (Ta), and tungsten (W) is selected from;
In the silicon-based alloy powder,
Based on the total number of atoms of the silicon, the first metal (M ₁ ) and the second metal (M ₂ ), the content of Si is 50 atomic% to 90 atomic%, and the content of _{the first metal (M 1 )} This 10 atomic % to 50 atomic %, the _{content of the second metal (M 2} ) is more than 0 atomic % to 10 atomic %,
Based on 100 parts by weight of the sum of the silicon, the first metal (M ₁ ), and the second metal (M ₂ ), the total content of C is 0.01 parts by weight to 20 parts by weight, and the total content of B is 0 The negative active material is in an amount of 20 parts by weight to 0.01 parts by weight to 50 parts by weight of the O content. According to claim 1,
An anode active material having an average particle diameter (D50) of the silicon-based alloy powder of 1 μm to 5 μm. 3. The method of claim 2,
An anode active material having an average particle diameter (D50) of the silicon nanoparticles of 10 nm to 150 nm. A lithium battery comprising the negative active material according to any one of claims 1 to 22.

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