High-Purity Aluminum Surface Layer Current Collector for High-Voltage Batteries
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Solution Overview
Problem
Nonaqueous electrolytic solution secondary batteries with positive electrode active materials showing operating potentials higher than 4.5 V experience significant battery capacity decrease due to aluminum (Al) elution from the current collector during high potential charge/discharge, leading to increased resistance and reduced performance.
Innovation Solution
A current collector with a surface layer of at least 99.85% aluminum content is used, forming a stable coat that prevents Al elution, combined with a base material of higher strength to maintain battery capacity and structural integrity during high potential charge/discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a positive electrode active material with operating potential higher than 4.5 V is used to achieve high energy density, then the energy density is improved, but aluminum elutes from the current collector during high potential charge/discharge, causing battery capacity to decrease
Solution Approach 1:
The current collector is constructed as a composite material with a base material (Al or Al alloy) and a surface layer with higher Al content (99.5% or more). This composite structure combines the electrical conductivity and cost-effectiveness of Al-based materials with the corrosion resistance and stability of high-purity Al surface layer, preventing Al elution during high potential charge/discharge while maintaining high energy density
Solution Approach 2:
The surface layer is specifically designed with higher aluminum content (99.5% or more) compared to the base material, creating a localized high-purity Al region at the surface. This local quality improvement provides enhanced stability and corrosion resistance where it is most needed (at the electrolyte interface) while allowing the bulk material to maintain its electrical conductivity and structural properties
2Reliability
If the surface layer is formed of high purity aluminum material to prevent Al elution, then the battery capacity stability is improved, but the strength of the current collector decreases
Solution Approach 1:
The current collector uses a composite structure where the base material provides mechanical strength (Al or Al alloy with appropriate composition) and the surface layer provides corrosion resistance and stability (high purity Al with 99.5% or more Al content). This composite approach allows each layer to optimize for its primary function without compromising the other
Solution Approach 2:
The high-purity aluminum surface layer is applied only where needed for electrochemical stability (at the surface in contact with electrolyte), while the base material maintains the structural integrity and strength requirements. This localized quality differentiation resolves the contradiction between surface stability and bulk strength
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 effectively suppresses the decrease in battery capacity and resistance, ensuring the battery can perform high potential charge/discharge cycles while maintaining sufficient strength, suitable for applications in hybrid, plug-in hybrid, and electric vehicles.
Implementation Method 1
a surface layer which is disposed, in the surface layer of the base material, at least in a region where the active material layer is not formed... a coat of Al2O3 or AlF3 is formed
Data Source
AI summary
A nonaqueous electrolytic solution secondary battery includes an electrode body that contains a positive electrode and a negative electrode. An upper limit operating potential of the positive electrode is 4.5 V or more based on metallic lithium. The positive electrode includes a current collector and an active material layer formed on the current collector. The current collector includes a base material and a surface layer disposed on a surface of the base material. The surface layer is disposed at least in a region where the active material layer is not formed on the surface of the base material. The surface layer is formed of an aluminum material having an aluminum content of 99.85% by mass or more. The base material is formed of a conductive material having strength larger than strength of the surface layer.