Negative Electrode Pre-Lithiation for Stable SEI and Cycle Life
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Solution Overview
Problem
Existing methods for pre-lithiation of lithium secondary battery negative electrodes are inefficient, leading to deterioration of cycle performance due to irreversible capacity loss and instability of the SEI film.
Innovation Solution
A method involving low-current charging and sufficient aging of the negative electrode after pre-lithiation, using a pre-lithiation solution and a lithium metal counter electrode, forms a stable SEI film, enhancing cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If pre-lithiation is performed using conventional methods, then lithium ions are supplied to the negative electrode, but irreversible capacity loss occurs due to SEI film formation and electrolyte decomposition
Solution Approach 1:
The patent applies preliminary action by performing pre-lithiation before battery assembly, where lithium ions are supplied to the negative electrode in advance. This pre-supplied lithium compensates for the lithium that will be consumed during the first charge cycle when the SEI film forms, thereby reducing the net irreversible capacity loss during normal battery operation
Solution Approach 2:
The patent converts the harmful effect of SEI film formation (which consumes lithium ions) into a benefit by performing pre-lithiation. The SEI film formation process, which normally causes irreversible capacity loss, is transformed into a controlled process that occurs during pre-lithiation, allowing the battery to achieve better cycle performance by having excess lithium available to form the protective SEI layer
2Reliability
If carbon-based materials are used as negative electrode active material, then safety is improved compared to metal lithium, but theoretical capacity is limited to about 400 mAh/g
Solution Approach 1:
The patent uses composite materials by combining carbon-based materials (such as graphite) with silicon-based materials (such as silicon oxide or silicon) in the negative electrode. This composite structure allows the battery to achieve higher theoretical capacity (up to 4,200 mAh/g for silicon) while maintaining the safety advantages of carbon-based materials, as the carbon component prevents the safety issues associated with pure metal lithium
3Quantity of substance
If silicon-based materials are used to replace carbon-based materials, then theoretical capacity increases to 4,200 mAh/g, but volume expansion and SEI film instability occur
Solution Approach 1:
The patent applies preliminary action by performing pre-lithiation to supply excess lithium ions to the negative electrode before battery assembly. This pre-supplied lithium ensures that when silicon-based materials expand and contract during cycling, there is always sufficient lithium available to maintain a stable SEI film, preventing electrolyte decomposition and maintaining electrode integrity throughout the battery's cycle life
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method results in a negative electrode with improved cycle performance by uniformly distributing lithium and forming a stable SEI film, reducing irreversible capacity loss and increasing the battery's operational stability.
Implementation Method 1
a process of charging the negative electrode at a low current during pre-lithiation
Implementation Method 2
a process of aging the negative electrode after the pre-lithiation for a sufficient time
Implementation Method 3
a process of intercalating a lithium ion of the positive electrode active material on the positive electrode in the negative electrode active material on the negative electrode and deintercalating the lithium ion
Implementation Method 4
an electrolyte decomposition reaction on the surface of the negative electrode active material, and an SEI film (solid electrolyte interface) is formed on the surface of the negative electrode active material by an electrochemical reaction through the electrolyte decomposition
Data Source
AI summary
The present invention relates to a method of producing a negative electrode for a lithium secondary battery, and the production method of the present invention includes a process of charging the negative electrode at a low current during pre-lithiation and a process of aging the negative electrode after the pre-lithiation for a sufficient time, thereby producing a negative electrode for a lithium secondary battery having excellent cycle performance.