Negative Electrode Pre-Lithiation for Lower Capacity Loss
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Solution Overview
Problem
Existing methods for pre-lithiation of negative electrodes in lithium secondary batteries suffer from irreversible capacity loss and instability due to oxidation when exposed to moisture or oxygen, leading to deteriorated cycle performance.
Innovation Solution
A method involving the formation of a negative electrode active material layer on a current collector, impregnation with a pre-lithiation solution, electrochemical charging at low current intensity, and aging for 90 minutes to 41 hours to produce a pre-lithiated electrode with improved cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If pre-lithiation is performed by depositing lithium on negative electrode or bringing negative electrode and lithium into direct contact, then initial irreversible capacity loss is reduced, but the lithiated material is vulnerable to oxidation and easily oxidized when exposed to moisture or oxygen, leading to deteriorated cycle performance
Solution Approach 1:
The patent introduces a polymer coating film as an intermediary protective layer between the lithiated negative electrode material and the external environment (moisture and oxygen). This coating film acts as a barrier that prevents direct contact between the sensitive lithiated material and oxidizing agents, thereby maintaining both the low irreversible capacity loss and the cycle performance
Solution Approach 2:
The patent creates an inert protective environment by forming a stable polymer coating film around the lithiated negative electrode. This coating film effectively isolates the lithiated material from moisture and oxygen in the air, creating a localized inert atmosphere that prevents oxidation while allowing the electrode to function properly
2Reliability
If carbon-based material is used as negative electrode active material, then safety is improved compared to metal lithium, but the theoretical capacity is limited to only about 400 mAh/g
Solution Approach 1:
The patent creates a composite negative electrode structure that combines carbon-based material with lithiated material. The carbon-based material provides safety and structural stability, while the lithiated material contributes high theoretical capacity. The polymer coating film binds these components together and protects the lithiated portions, achieving both safety and high capacity
3Quantity of substance
If silicon-based material is used to replace carbon-based material, then theoretical capacity is increased to 4,200 mAh/g, but volume expansion occurs during charge/discharge cycles affecting structural stability
Solution Approach 1:
The patent employs a flexible polymer coating film that can accommodate the volume expansion and contraction of silicon-based materials during charge/discharge cycles. This thin film structure provides mechanical flexibility while maintaining protective function, allowing the high-capacity silicon material to expand without compromising structural stability
4Reliability
If SEI film is formed on negative electrode surface through electrolyte decomposition, then ion tunnel function is achieved, but many lithium ions are consumed causing irreversible capacity loss
Solution Approach 1:
The patent performs pre-lithiation before battery assembly, which preliminarily compensates for the lithium ions that will be consumed during SEI film formation. By adding extra lithium in advance, the subsequent SEI formation process does not result in net capacity loss, as the consumed lithium is replaced by the pre-added lithium
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
This method reduces irreversible capacity loss and enhances the stability of the negative electrode, resulting in improved cycle performance and oxidation resistance by uniformly distributing lithium ions and forming a stable polymer coating film.
Implementation Method 1
electrochemically charging the negative electrode at a low current in a pre-lithiation process
Implementation Method 2
uniformly distributing lithium ions
Implementation Method 3
aging the negative electrode after the pre-lithiation for a sufficient time
Implementation Method 4
forming a stable polymer coating film
Implementation Method 5
impregnation with a pre-lithiation solution
Data Source
AI summary
A method of producing a negative electrode for a lithium secondary battery. 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.