Battery Separator Coating With Mg2+ Crosslinking for Cycle Stability
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Solution Overview
Problem
The formation of an SEI film during the initial charging process consumes a significant amount of active lithium, leading to low initial efficiency and reduced energy density in batteries, particularly in negative electrodes with materials like silicon, and poor binding strength between the negative electrode and separator results in battery deformation.
Innovation Solution
Incorporating a functional layer with Mg2+ in the negative electrode and a polymer material in the separator coating that performs a coordination crosslinking reaction, enhancing the binding strength and ionic conductivity between the negative electrode and separator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SEI film is formed during initial charging process, then negative electrode protection is improved, but active lithium is consumed leading to decreased initial efficiency and energy density
Solution Approach 1:
The patent introduces a pre-embedded layer containing magnesium particles before the negative active substance layer. During initial charging, magnesium reacts with electrolyte to form MgF2 and other compounds that pre-form protective films on the negative electrode surface, preventing excessive SEI formation and active lithium consumption. This preliminary protective action occurs before the negative electrode is fully assembled, solving the contradiction by preparing the surface in advance to reduce subsequent lithium loss.
Solution Approach 2:
The pre-embedded layer acts as an intermediary between the current collector and the negative active substance layer. It contains magnesium particles that react with the electrolyte to form protective compounds (MgF2, MgO, etc.) that serve as a buffer layer, preventing direct and excessive SEI formation on the negative electrode. This intermediary layer reduces active lithium consumption while maintaining electrode protection.
2Reliability
If conventional separator is used, then separation function is achieved, but binding strength between negative electrode and separator is insufficient leading to battery deformation
Solution Approach 1:
The separator is designed as a composite structure with a base film layer and a coating layer. The coating layer contains polymer material (such as polyacrylic acid, polyacrylamide, or carboxymethyl cellulose) that can chemically interact with the pre-embedded layer. This composite structure provides both the separation function of the base film and the enhanced binding strength through the functional coating layer, resolving the contradiction between separation performance and mechanical bonding.
Solution Approach 2:
The patent modifies the separator by adding a coating layer with specific chemical properties (polymer materials with functional groups). This changes the surface parameters of the separator to enable chemical interaction with the pre-embedded layer, transforming the physical adhesion into chemical bonding and significantly improving binding strength while maintaining separation function.
3Strength
If polymer material with bonding performance is used in coating layer, then binding strength is improved, but ionic conductivity may be reduced
Solution Approach 1:
The coating layer uses polymer materials with specific local functional groups (carboxyl, amide, aromatic acid, or sulfonate groups) that provide bonding capability. These functional groups are localized at the interface with the pre-embedded layer, providing strong chemical bonding where needed, while the bulk of the polymer material maintains porosity and ionic conductivity pathways for lithium ion transport through the separator.
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 prevents battery deformation by increasing the binding strength and reducing internal resistance, thereby enhancing fast charging performance.
Implementation Method 1
the polymer material in the coating layer performs a coordination crosslinking reaction with the Mg2+ in the functional layer, so as to effectively increase binding strength between the negative electrode plate and the separator
Implementation Method 2
after ionization of the polymer material, ionic conductivity performance of the polymer material can be effectively improved, and internal resistance of the battery is reduced
Data Source
AI summary
This application provides a battery, including a negative electrode plate and a separator. The negative electrode plate includes a negative active substance layer and a functional layer that are stacked. The functional layer includes Mg2+, where some of the Mg2+ is embedded in the negative active substance layer. The separator includes a base film and a coating layer located on a surface of the base film, and the coating layer bonds the base film and the functional layer. The coating layer includes a polymer material. The polymer material is coordination-crosslinked with at least some of the remaining Mg2+ in the functional layer. The polymer material in the coating layer performs a coordination crosslinking reaction with the Mg2+ in the functional layer, so as to effectively increase binding strength between the negative electrode plate and the separator, thereby helping prevent deformation of the battery during a cycle process.