Method for preparing silicon anode active material in which nano-silicon mixture is inserted into pores of coffee grounds
A method for preparing a silicon anode active material in which a nano-silicon mixture is inserted into pores of coffee grounds according to the present disclosure can contribute to the protection of the natural environment through the preparation of a high-capacity silicon anode active material for a lithium secondary battery, which is prepared using coffee grounds that are an environmental pollutant, and has an effect of lowering the preparation cost of a lithium secondary battery anode material with the high-capacity silicon anode active material using coffee grounds by including the steps of: a) preparing nano-silicon; b) preparing an anionic surfactant; c) preparing silane; d) preparing a mixed dispersion based on ultrapure distilled water; e) drying and preparing coffee grounds; f) mixing polyvinyl alcohol into a mixed dispersion; g) mixing polyamic acid into the mixed dispersion; h) mixing graphite into the mixed dispersion; i) mixing vegetable oil into the mixed dispersion; j) final mixed dispersion heat treatment process step; k) obtaining a silicon active material of a certain size using an ultrasonic vibrating screen; l) obtaining a silicon anode active material final product by inserting nano-silicon into the pores of the coffee grounds; and m) obtaining a silicon anode active material in which a nano-silicon mixture (SiO 2 , SiC) is inserted into the pores of the coffee grounds.
1 . A method comprising the steps of:
a) preparing nano-silicon;
b) preparing an anionic surfactant;
c) preparing silane;
d) preparing a first mixed dispersion by mixing and dispersing the nano-silicon, the anionic surfactant, and the silane in tertiary distilled water;
e) preparing a second mixed dispersion by mixing and dispersing dried coffee grounds in the first mixed dispersion;
f) preparing a third mixed dispersion by mixing and dispersing polyvinyl alcohol in the second mixed dispersion;
g) preparing a fourth mixed dispersion by mixing and dispersing polyamic acid in the third mixed dispersion;
h) preparing a fifth mixed dispersion by mixing and dispersing graphite in the fourth mixed dispersion;
i) preparing a sixth mixed dispersion by mixing and dispersing a vegetable oil in the fifth mixed dispersion;
j) heat-treating the sixth mixed dispersion to cause the nano-silicon to be inserted into pores of the coffee grounds and to carbonize a mixture of the coffee grounds and the nano-silicon; and
k) pulverizing the carbonized mixture of the coffee grounds and the nano-silicon and selecting and obtaining a portion of the pulverized carbonized mixture using an ultrasonic vibrating screen to obtain a silicon anode active material.
2 . The method of claim 1 , wherein the step e) is preparing the second mixed dispersion by mixing and dispersing the dried coffee grounds in the first mixed dispersion using a high voltage pulse dispersion device, and the step j) is a step of heat-treating the sixth mixed dispersion using a ball mill device.
3 . The method of claim 2 , wherein the high voltage pulse dispersion device of the step e) continuously applies a high voltage charged from a capacitor to an electrode so that a silicon wire included in the high voltage pulse dispersion device causes an electric explosion in a liquid, and through this, the silicon wire included in the high voltage pulse dispersion device is nano-powdered and dispersed,
the high voltage pulse dispersion device has an ultrasonic generator additionally configured therein to increase a dispersion effect,
and the step e) is additionally putting polyvinylpyrrolidone as a dispersant to increase the dispersion effect.
4 . The method of claim 2 , wherein the ball mill device of the step j) includes an ultrasonic generator added to a first plate portion forming a space inner wall where balls and a dispersion collide, and
a heating unit including a thermoelectric element is provided on a bottom of the first plate portion so that dispersion and heat treatment processes are proceeded together.
5 . The method of claim 2 , wherein the ball mill device of the step j) further includes a first plate portion forming a space inner wall where balls and a dispersion collide, and a second plate portion spaced apart from the first plate portion and configured so that an air pump, an inlet, and a thermoelectric element are inserted into the second plate portion, and
a passage unit through which heated air moves is provided in a separated space between the first plate portion and the second plate portion, thereby uniformly heating the ball mill device.
6 . The method of claim 1 , wherein the step a) includes the steps of:
a-1) preparing silicon dioxide by drying a mixture in an amount of 1 to 0.68% by weight of the total 100% by weight of tertiary distilled water at 100 to 130° C.;
a-2) preparing silicon carbide by drying a mixture in an amount of 1 to 0.26% by weight of the total 100% by weight of the tertiary distilled water at 100 to 130° C.; and
a-3) drying the silicon to remove moisture contained in the silicon.
7 . The method of claim 1 , wherein the step b) is characterized in that the anionic surfactant in which anions generated by dissociation in water are adsorbed on surface of an aqueous solution to lower a surface tension is any one component of sodium lauryl ether sulfate, sodium α-olefin sulfonate, and alkyldimethylamine oxide, and is used in a mixing amount of 1 to 7.5% by weight of the total 100% by weight of the tertiary distilled water.
8 . The method of claim 1 , wherein the step c) is using methyltrimethoxysilane: (CH3O)3SiCH3 to allow an inorganic surface to have hydrophobic properties in a mixing amount of 1 to 6.25% by weight of the total 100% by weight of tertiary distilled water.
9 . The method of claim 1 , wherein the step f) is mixing the polyvinyl alcohol in an amount of 1 to 0.5% by weight of the total 100% by weight of the tertiary distilled water.
10 . The method of claim 9 , wherein the step h) is characterized in that the graphite is natural graphite, and is mixed in an amount of 1 to 15% by weight of the total 100% by weight of the tertiary distilled water.
11 . The method of claim 1 , wherein the step g) is mixing the polyamic acid in an amount of 1 to 1.37% by weight of the total 100% by weight of the tertiary distilled water.
12 . The method of claim 1 , wherein the step i) is mixing the vegetable oil in an amount of 1 to 7.5% by weight of the total 100% by weight of the tertiary distilled water.
13 . The method of claim 1 , wherein the step j) is a sixth mixed dispersion final heat treatment process, and includes the steps of:
j-1) primarily performing drying at 300 to 380° C.; and
j-2) secondly performing heat treatment at 800 to 900° C.
14 . The method of claim 1 , wherein, in step k), the carbonized mixture of the coffee grounds and the nano-silicon is pulverized with an automatic grinding mill and screened using an ultrasonic vibrating screen sieve so that the silicon anode active material is obtained.