Lithium-Composite Separator Coating for Safe Pre-Lithiation
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Solution Overview
Problem
Lithium secondary batteries face challenges in maintaining initial efficiency and cycle life due to irreversible capacity loss at the negative electrode, particularly when using Si-based materials, which results in lithium depletion and instability issues.
Innovation Solution
A separator with a coating layer of lithium-containing composite particles, including a lithiated compound and a solid electrolyte interface (SEI) film, is applied to supplement the irreversible capacity by pre-lithiating the negative electrode during charge, using a porous polymer substrate and a binder to stabilize the coating layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pre-lithiation is carried out using lithium metal, then initial reversibility and capacity are improved, but safety risks increase due to fire and explosion hazards
Solution Approach 1:
The patent uses a separator with a coating layer containing lithium-containing composite particles as an intermediary to provide pre-lithiation function. Instead of directly using lithium metal which causes safety issues, the lithium is embedded in composite particles (lithiated compound + SEI film) coated on the separator, which acts as a mediator between the negative electrode and the lithium source, eliminating direct contact and safety hazards while maintaining the pre-lithiation effect
Solution Approach 2:
The lithium-containing composite particles in the coating layer serve as a disposable lithium source. These particles are designed to gradually release lithium ions during initial charging cycles to compensate for irreversible capacity loss, then are consumed and replaced in subsequent battery cycles. This approach replaces expensive and dangerous lithium metal with a controlled, consumable coating layer
2Quantity of substance
If Si-based material is used for negative electrode to achieve high capacity, then battery capacity is improved, but initial efficiency decreases due to high irreversible capacity
Solution Approach 1:
The patent applies preliminary action by pre-coating the separator with lithium-containing composite particles before battery assembly. This coating layer proactively supplies lithium ions during initial charging cycles to compensate for the high irreversible capacity consumption of Si-based negative electrodes, ensuring that sufficient lithium remains for subsequent reversible cycling and improving initial efficiency before the battery enters normal operation
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 solution enhances initial reversibility and efficiency by intercalating lithium ions from the coating layer into the negative electrode, improving battery life and stability while avoiding the risks associated with handling lithium metal.
Implementation Method 1
the passivation film comprises a solid electrolyte interface (SEI)
Implementation Method 2
During charge, the lithium ions intercalated to the positive electrode move to the negative electrode through the electrolyte
Data Source
AI summary
A separator including: a porous polymer substrate having a plurality of pores; and a coating layer formed on at least one surface of the porous polymer substrate, and including a plurality of lithium-containing composite particles and a binder positioned on the whole or a part of the surface of the lithium-containing composite particles to connect and fix the lithium-containing composite particles with each other, wherein the lithium-containing composite particles includes a lithiated compound and a passivation film formed on the surface of the lithiated compound, and the passivation film includes a solid electrolyte interface (SEI). A lithium secondary battery including the separator and a method for manufacturing the lithium secondary battery are also provided.