Negative Electrode Protective Layer for Battery Safety
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in achieving safety without significantly reducing charged and discharged capacities, particularly in maintaining a thin protective layer that minimizes internal resistance while ensuring safety against internal short-circuiting.
Innovation Solution
A negative electrode with a surface roughness reduction by using a first negative electrode active material with an aspect ratio between two and eight, combined with a ceramic powder protective layer and a water-based binder, to create a uniform protective layer that enhances safety without compromising capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer is provided on the active material layer to enhance safety, then safety is improved, but the thickness of the protective layer increases internal resistance and lowers charged and discharged capacities
Solution Approach 1:
The patent changes the physical and chemical parameters of the protective layer by specifying ceramic powder particle size (0.1-2.0 μm), composition ratios (ceramic powder 90-99 wt%, binder 1-10 wt%), and layer thickness (1-10 μm) to optimize both safety and capacity retention
Solution Approach 2:
The protective layer is formed as a composite material combining ceramic powder (providing safety and thermal stability) with binder material (providing adhesion and flexibility), creating a multifunctional coating that balances safety enhancement with minimal impact on electrochemical performance
2Use of energy by moving object
If the protective layer is made thinner to maintain energy density, then energy density is improved, but safety is compromised
Solution Approach 1:
The patent optimizes the thickness parameter to 1-10 μm and ceramic powder particle size to 0.1-2.0 μm to achieve maximum protective effect per unit thickness, thereby maintaining high energy density while ensuring safety
3Reliability
If the surface coarseness of the active material layer is large, then the protective layer can be made thicker for safety, but the charged and discharged capacities are extremely lowered
Solution Approach 1:
The patent specifies ceramic powder particle size of 0.1-2.0 μm and layer thickness of 1-10 μm to create a uniformly thin protective layer that does not significantly reduce capacity while providing adequate safety protection
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 configuration results in a nonaqueous electrolyte secondary battery with improved safety and maintained capacity, as the uniform protective layer inhibits internal short-circuiting and reduces thickness unevenness, thereby enhancing the battery's overall performance.
Implementation Method 1
a protective layer comprising a ceramic powder
Data Source
AI summary
The negative electrode includes a current collector, a negative electrode active material layer arranged on a surface of the current collector, and a protective layer arranged on a surface of the negative electrode active material layer. The negative electrode active material layer includes a first negative electrode active material having an aspect ratio defined as “a”/“b” to fall in a range of from two or more to eight or less when a length of the major axis is defined “a” and a length of the minor axis is defined “b.” The protective layer includes a ceramic powder.