Separator-Based Lithium Transfer for Uniform Electrode Pre-Lithiation
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Solution Overview
Problem
The existing methods for pre-lithiation of silicon-based negative electrodes in lithium secondary batteries face challenges such as high costs, safety concerns due to high-temperature processes, and difficulties in uniformly controlling the initial irreversible capacity, leading to reduced battery capacity and cycle life.
Innovation Solution
A method involving a transfer laminate with a base layer, surface protection layer, and lithium metal layer is used, where the lithium metal layer is transferred to a separator instead of directly onto the electrode active material, allowing for controlled pre-lithiation without additional buffer layers, thus preventing exposure to air and enabling efficient lithium transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrode active material is used to improve capacity, then energy density is improved, but volume change occurs during lithium ion intercalation/deintercalation resulting in deterioration of mechanical stability and impaired cycle characteristics
Solution Approach 1:
The negative electrode active material layer is divided into a silicon-based negative electrode active material layer and a graphite negative electrode active material layer. The graphite layer acts as a buffer that accommodates the volume expansion of silicon during lithium intercalation, preventing mechanical deterioration while maintaining high capacity.
Solution Approach 2:
A composite negative electrode structure is formed by combining silicon-based negative electrode active material with graphite negative electrode active material. This composite structure leverages the high capacity of silicon while using graphite's structural stability to mitigate volume change issues.
2Quantity of substance
If pre-lithiation method of manufacturing electrode after lithiation by physicochemical method is used, then initial irreversible capacity is reduced, but safety concerns arise due to high-temperature processes
Solution Approach 1:
Lithium metal layer is deposited on the separator in advance before battery assembly. This preliminary action allows controlled lithium transfer to the negative electrode during initial charging, compensating for initial irreversible capacity loss without requiring high-temperature physicochemical treatment.
Solution Approach 2:
The separator serves as an intermediary carrier for lithium metal. Instead of directly treating the negative electrode at high temperature, lithium is first deposited on the separator and then transferred to the negative electrode during normal charging conditions, eliminating safety concerns.
3Quantity of substance
If lithium metal layer is transferred directly onto electrode active material, then pre-lithiation is achieved, but additional buffer layers are required increasing device complexity
Solution Approach 1:
The separator performs multiple functions: it acts as both the separator between electrodes and as the carrier for lithium metal layer. By depositing lithium on the separator, the need for separate buffer layers is eliminated, reducing device complexity while achieving pre-lithiation.
4Quantity of substance
If conventional pre-lithiation methods are used, then manufacturing cost increases, but if no pre-lithiation is performed, battery capacity and cycle life are rapidly reduced
Solution Approach 1:
The separator serves as an intermediary that enables pre-lithiation without requiring complex additional processing steps. Lithium metal is deposited on the separator using simple vacuum deposition, and the separator naturally transfers lithium to the negative electrode during assembly, reducing manufacturing cost while improving battery performance.
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 approach allows for uniform pre-lithiation of the electrodes, reducing manufacturing costs and electrode resistance, while improving the initial charge capacity and cycle life of the battery by controlling the pre-lithiation rate effectively.
Implementation Method 1
transferring the surface protection layer and the lithium metal layer to a separator so that the lithium metal layer comes into contact with the separator
Implementation Method 2
lithium discharged from the positive electrode is intercalated into the negative electrode during charging, and is deintercalated from the negative electrode to return to the positive electrode again during discharging
Data Source
AI summary
The present invention relates to a method for manufacturing an electrode assembly, in which after transferring a transfer laminate in which a base layer, a surface protection layer, and a lithium metal layer are sequentially laminated so that the lithium metal layer is brought into contact with a separator, the separator onto which the lithium metal layer is transferred is brought into contact with the surface of the electrode layer, and the surface protection layer is made to face an electrode.