Ceramic-Coated Negative Electrode for Thin Insulating Battery Stacks
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Solution Overview
Problem
The challenge is to develop a negative electrode for a unified stack cell lithium secondary battery that maintains reinforced insulation properties while minimizing the thickness of the ceramic separating layer to enhance energy density and safety.
Innovation Solution
The solution involves a negative electrode with a negative electrode active material layer having a controlled arithmetic average surface roughness (Ra) of 0.01 μm to 0.3 μm, and a ceramic separating layer with a thickness of 1 μm to 30 μm, which is formed on the negative electrode active material layer to improve insulation and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the thickness of the ceramic separating layer is decreased to improve energy density, then energy density is improved, but insulating properties and safety are deteriorated
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thickness of the ceramic separating layer within a specific range (1-30 μm) and controlling the surface roughness of the negative electrode active material layer (Ra ≤ 0.05 μm). This optimization of dimensional parameters allows the ceramic layer to maintain adequate insulating properties while being thin enough to achieve high energy density, directly resolving the contradiction between thickness reduction and insulating performance maintenance.
2Productivity
If the thickness of the separator is decreased to promote material movement and achieve high power, then ionic conductivity is improved, but pinholes may be formed and the separator may be broken to increase the possibility of inducing short
Solution Approach 1:
The patent utilizes porous ceramic materials as the separating layer, which inherently provide both high ionic conductivity through their porous structure and mechanical integrity. The porous ceramic layer allows efficient lithium ion transport while the ceramic material's structural strength prevents pinhole formation and breakage that plague thin polyolefin separators, thus resolving the contradiction between ionic conductivity and separator integrity.
Solution Approach 2:
The patent employs composite material structure by combining the ceramic separating layer with the negative electrode active material layer, where the ceramic layer serves dual functions as both separator and protective coating. This composite approach allows the system to achieve high ionic conductivity through the porous ceramic structure while maintaining mechanical strength and preventing short circuits, overcoming the limitations of conventional thin separators.
3Reliability
If a ceramic layer is used instead of the conventional polyolefin separator, then pinhole generation is prevented, but the ceramic layer is required to have a thickness of a certain degree or greater to maintain insulating properties
Solution Approach 1:
The patent resolves this contradiction by optimizing the thickness parameter of the ceramic layer to a specific range (1-30 μm), which is thinner than conventional ceramic separators but sufficient to maintain pinhole prevention and insulating properties. This precise parameter control allows the ceramic layer to provide reliable pinhole-free separation while minimizing thickness to achieve high energy density.
Solution Approach 2:
The patent applies local quality by forming the ceramic separating layer specifically on the negative electrode active material layer where it is most needed for pinhole prevention and insulation. This localized ceramic coating approach provides pinhole-free separation at the critical electrode interface while keeping the overall ceramic layer thickness minimal, thus preventing pinholes without requiring excessive thickness throughout the entire separator structure.
Data Source
AI summary
Provided are a negative electrode for a lithium secondary battery having reinforced insulating properties, which comprises a negative electrode active material layer; and a ceramic separating layer formed on the negative electrode active material layer, wherein the negative electrode active material layer has an arithmetic average surface roughness (Ra) of 0.01 μm to 0.3 μm, and the ceramic separating layer has a thickness of 1 μm to 30 μm, and a lithium secondary battery comprising the same.