Method of manufacturing negative electrode

A method of manufacturing a negative electrode, comprising:

• preparing a negative electrode roll on which a negative electrode structure is wound, the negative electrode structure comprising a negative electrode current collector, a first negative electrode active material layer on one surface of the negative electrode current collector, and a second negative electrode active material layer on the other surface of the negative electrode current collector, wherein the first negative electrode active material layer comprises first side parts partitioned at both sides of the first negative electrode active material layer and a first central part partitioned by excluding the first side parts, and the second negative electrode active material layer comprises second side parts partitioned at both sides of the second negative electrode active material layer and a second central part partitioned by excluding the second side parts;
• preparing a pre-lithiation bath comprising a pre-lithiation solution, wherein the pre-lithiation bath is sequentially divided into an impregnation section and a pre-lithiation section;
• impregnating the negative electrode structure with the pre-lithiation solution while unwinding the negative electrode structure from the negative electrode roll and moving the negative electrode structure through the impregnation section;
• and
• pre-lithiating the negative electrode structure through electrochemical charging while moving the negative electrode structure through the pre-lithiation section,
• wherein during the pre-lithiating step, the pre-lithiation section comprises a first section and a second section, the first central part and the second central part are electrochemically charged in the first section, the first side parts and the second side parts are electrochemically charged in the second section, the first central part, the first side parts, the second central part, and the second side parts are sequentially electrochemically charged in one or more cycles in any order, a charge current applied to the first central part is higher than a charge current applied to the first side parts, and a charge current applied to the second central part is higher than a charge current applied to the second side parts,
• wherein a first lithium metal counter electrode faces and is spaced apart from the first and second central parts of the first and second negative electrode active material layers in the first section,
• a second lithium metal counter electrode faces and is spaced apart from the first and second side parts of the first and second negative electrode active material layers in the second section,
• the first lithium metal counter electrode and the negative electrode structure are connected to each other through a first electrochemical charger/discharger, the second lithium metal counter electrode and the negative electrode structure are connected to each other through a second electrochemical charger/discharger, and
• the pre-lithiation is performed by setting a charge current applied from the first electrochemical charger/discharger to be higher than a charge current applied from the second electrochemical charger/discharger and alternately electrochemically charging the first and second central parts and the first and second side parts of the negative electrode structure in one or more cycles while alternately operating the first electrochemical charger/discharger and the second electrochemical charger/discharger.