Negative electrode and secondary battery including the negative electrode

A method of preparing a negative electrode, the method comprising:

• preparing a conductive agent dispersion (S1);
• forming a negative electrode slurry including the conductive agent dispersion, a negative electrode active material, a binder, and a solvent (S2), wherein the preparing of the conductive agent dispersion (Sl) comprises:
• preparing a mixed solution containing a dispersion medium, a dispersant, and bundle type single-walled carbon nanotubes (Sl-1);
• and
• forming a carbon nanotube structure, in which a plurality of single-walled carbon nanotube units are bonded side by side, by dispersing the bundle type single-walled carbon nanotubes by applying a shear force to the mixed solution through a high-pressure homogenizer (Sl-2),
• wherein the carbon nanotube structure has an average length of 1 μm to 20 μm, and QBR according to Equation 1 is in a range of greater than 1 to 1.75:
• QBR
• =
• Bs
• /
• Bf
• [
• Equation
• ⁢
• 1
• ]
• the negative electrode comprises a negative electrode active material layer that is formed from the negative electrode slurry,
• wherein Bs is an average value of an amount of binder which is measured in a range from an upper surface of the negative electrode active material layer to a distance corresponding to 15% of a total thickness of the negative electrode active material layer in a direction toward a lower surface of the negative electrode active material layer, and
• wherein Bf is an average value of an amount of binder which is measured in a range from the lower surface of the negative electrode active material layer to a distance corresponding to 15% of the total thickness of the negative electrode active material layer in a direction toward the upper surface of the negative electrode active material layer.