Negative Electrode Pre-Lithiation with Controlled SEI Formation
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Solution Overview
Problem
Existing pre-lithiation methods for negative electrodes in secondary batteries suffer from inefficient SEI film composition adjustment during electrochemical charging, leading to reduced battery capacity and cycle lifespan due to lithium ion consumption and irreversible reactions.
Innovation Solution
A pre-lithiation apparatus and method that includes a reactor with a pre-lithiation solution, a lithium metal counter electrode spaced 7 to 15 mm apart from the negative electrode, and a charge and discharge unit, allowing for controlled electrochemical charging to form an optimized SEI film with a specific Li2CO3 to ROCO2Li content ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If lithium metal is directly contacted with the negative electrode surface, then pre-lithiation efficiency is improved, but battery safety deteriorates due to uncontrolled SEI formation
Solution Approach 1:
A porous separator is introduced as an intermediary between the lithium metal anode and the negative electrode. This separator allows controlled ion transport while preventing direct contact between lithium metal and the negative electrode, thus maintaining safety while enabling pre-lithiation functionality.
Solution Approach 2:
The separator is designed with different properties in different regions: it is porous to allow lithium ion transport where needed, but provides physical separation to prevent direct contact. This localized variation in permeability and structural properties enables simultaneous achievement of pre-lithiation efficiency and safety.
2Stability of the object's composition
If the distance between lithium metal and negative electrode is increased, then SEI film composition is improved, but pre-lithiation effectiveness deteriorates
Solution Approach 1:
The distance parameter between lithium metal and negative electrode is optimized to a specific range (0.5-2.0 mm) to achieve the desired SEI film composition while maintaining pre-lithiation effectiveness. This parameter optimization resolves the contradiction by finding the optimal balance point.
Solution Approach 2:
The porous separator acts as a mediator that maintains a controlled distance between lithium metal and the negative electrode, enabling consistent SEI film formation with improved composition while ensuring sufficient lithium ion transport for effective pre-lithiation.
3Stability of the object's composition
If electrochemical charging is performed with lithium metal spaced apart from the negative electrode, then SEI film composition can be controlled, but charging time increases
Solution Approach 1:
The charging current density is optimized in conjunction with the controlled distance to reduce charging time while maintaining the improved SEI film composition. By adjusting these parameters together, the contradiction between composition control and charging speed is resolved.
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
Improves initial efficiency and cycle characteristics of the battery by preventing redox reactions and ensuring uniform lithium ion distribution through controlled SEI film formation.
Implementation Method 1
a method of connecting lithium metal with the negative electrode and electrochemically charging the negative electrode
Implementation Method 2
a passive film such as a solid electrolyte interface (SEI) layer is formed on the surface of the negative electrode during the initial charge
Implementation Method 3
pre-lithiating the negative electrode through inserting lithium into the negative electrode
Data Source
AI summary
An apparatus for pre-lithiating a negative electrode includes a pre-lithiation reactor sequentially divided into an impregnation section, a pre-lithiation section and an aging section, and accommodates a pre-lithiation solution in which a negative electrode structure is moved; a negative electrode roll arranged outside the pre-lithiation solution and on which the negative electrode structure before being moved is wound; a lithium metal counter electrode arranged in the pre-lithiation solution in the pre-lithiation section and is spaced apart from the negative electrode structure by a predetermined distance to face the negative electrode structure which is moved in the pre-lithiation solution; and a charge and discharge unit connected to the negative electrode structure and the lithium metal counter electrode. A method for pre-lithiating the negative electrode is also provided.