Positive Electrode Insulating Layer With Wet Adhesion in Electrolyte
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Solution Overview
Problem
Conventional insulating layers in lithium secondary batteries exhibit degraded wet adhesion when immersed in liquid electrolyte, leading to lithium ion migration and capacity expression, which can degrade battery stability.
Innovation Solution
A positive electrode for lithium secondary batteries is designed with an insulating layer prepared using an aqueous binder dispersed in a non-aqueous solvent, covering the non-coated part of the current collector and active material layer, and optionally including inorganic particles to enhance adhesion and electrical insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional insulating layer is applied to the electrode, then electrical insulation is provided, but wet adhesion degrades when immersed in liquid electrolyte
Solution Approach 1:
The insulating layer uses a composite structure combining inorganic particles (such as alumina, silica, or boehmite) with an organic binder resin. This composite material provides both electrical insulation through the inorganic particles and excellent wet adhesion through the binder resin matrix, resolving the contradiction between insulation performance and adhesion strength in the liquid electrolyte environment.
Solution Approach 2:
The patent optimizes parameters including the particle size distribution of inorganic particles (combining fine and coarse particles), the molecular weight and type of binder resin, and the weight ratio of inorganic particles to binder (typically 90:10 to 50:50). These parameter changes enable the insulating layer to maintain both high electrical insulation and strong wet adhesion simultaneously.
2Reliability
If the insulating layer blocks lithium ion migration, then battery stability improves, but capacity expression is reduced
Solution Approach 1:
The insulating layer is applied selectively only to specific regions of the electrode where it is most needed - typically the edges, corners, and areas prone to short circuits or dendrite formation. The overlay region (central active material area) maintains full lithium ion conductivity. This local application strategy provides stability enhancement where required while preserving capacity expression in the active regions.
Solution Approach 2:
The insulating layer acts as a protective copy or shield over vulnerable electrode regions, replicating the insulation function without interfering with the electrochemical activity of the underlying active material. It creates a protective interface that prevents direct contact between electrodes while allowing ionic transport where needed.
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 insulating layer with excellent wet adhesion blocks lithium ion migration, improving battery stability and thermal safety by preventing capacity expression and thermal expansion.
Implementation Method 1
an insulating layer prepared with an aqueous binder dispersed in a non-aqueous solvent
Implementation Method 2
the insulating layer having excellent wet adhesion... blocks the migration of lithium ions in the overlay region of the electrode
Implementation Method 3
the insulating layer having excellent wet adhesion... degraded adhesion (hereinafter, referred to as wet adhesion) while being immersed in a liquid electrolyte
Data Source
AI summary
A positive electrode for a lithium secondary battery includes an insulating layer having excellent wet adhesion provide an advantage in that migration of lithium ions in an overlay region of the electrode can be blocked to suppress capacity expression due to the insulating layer having excellent wet adhesion in a liquid electrolyte.