Silicon Anode Pre-Lithiation Under Pressure for Volume Stability
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Solution Overview
Problem
Silicon-based negative electrodes in lithium secondary batteries experience volume changes during lithium ion insertion and removal, leading to mechanical instability, impaired cycle characteristics, and increased initial irreversible capacity, which reduces battery capacity and cycle life.
Innovation Solution
A pre-lithiation method involving direct contact of lithium metal with the negative electrode in an electrolyte, followed by pressure application to stabilize the electrode, with specific force and time ranges to minimize volume changes and improve cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based materials are used as negative electrode active material to improve capacity density, then the energy density of the negative electrode is improved, but volume change occurs during lithium ion insertion/removal resulting in mechanical instability and impaired cycle characteristics
Solution Approach 1:
The patent applies pre-lithiation treatment before battery assembly, where lithium metal is brought into direct contact with the negative electrode and pressure is applied. This preliminary action compensates for future volume changes by pre-establishing a stable electrode structure, thereby maintaining mechanical stability while preserving the high capacity density of silicon-based materials
2Quantity of substance
If silicon-based negative electrode active material is used to increase capacity, then energy density is improved, but initial irreversible capacity becomes large resulting in rapid reduction of battery capacity and cycle life
Solution Approach 1:
The pre-lithiation process is performed before battery assembly by bringing lithium metal into direct contact with the negative electrode under pressure. This preliminary action compensates for the initial irreversible capacity loss by pre-inserting lithium, thereby reducing the overall energy loss during subsequent charging and discharging cycles while maintaining the high capacity of silicon-based materials
3Loss of energy
If pre-lithiation is performed by direct contact of lithium metal with negative electrode, then initial irreversible capacity is reduced, but volume change during lithium ion migration may still reduce capacity and cycle
Solution Approach 1:
Pressure is applied during the pre-lithiation process before battery assembly, which compactsthe negative electrode structure in advance. This preliminary compaction minimizes subsequent volume changes during lithium ion migration, thereby maintaining both reduced initial irreversible capacity and improved volume stability for enhanced cycle life
Solution Approach 2:
The patent applies pressure as a physical parameter during pre-lithiation to compact the negative electrode. This parameter change stabilizes the electrode structure by reducing porosity and increasing density, thereby minimizing volume changes during subsequent lithium ion insertion and removal cycles while maintaining the benefits of reduced initial irreversible capacity
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 effectively reduces volume changes and initial irreversible capacity, enhancing the cycle performance and capacity retention rate of the secondary battery by stabilizing the electrode structure.
Implementation Method 1
even after lithiation, there may be a volume change as lithium ions migrate through the diffusion in the negative electrode
Implementation Method 2
the negative electrode is pressed at high pressure during the stabilization (aging) time after removing the lithium metal
Data Source
Figure 1~2
AI summary
The present invention provides a method of pre-lithiating an electrode for a secondary battery, the method including: a first step of bringing a lithium metal directly into contact with an electrode in an electrolyte and applying a pressure to the electrode to be pre-lithiated; and a second step of removing the lithium metal and then applying a pressure to the pre-lithiated electrode to perform a stabilization process. The electrode for the secondary battery after going through the pre-lithiation step provided in the present invention can relieve the volume change of the electrode and reduce the contact loss of the electrode.