Electrolytic Copper Foil with Protective Layers for Battery Anodes
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Solution Overview
Problem
Lithium secondary batteries face issues with the expansion of composite active materials during charging and discharging, leading to breakage of electrolytic copper foils, and the thin foils used are prone to curling or wrinkling, making handling and coating difficult, which affects the durability and efficiency of the batteries.
Innovation Solution
An electrolytic copper foil with a matte and shiny surface, coated with protective layers containing chromium, silane, or nitrogen compounds, is developed, with a controlled coefficient of thermal expansion, tensile strength, and surface roughness, allowing for improved handleability and durability, and a manufacturing method involving electroplating with specific conditions to maintain these properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a thin electrolytic copper foil (10 μm or less) is used to manufacture an anode, then the battery size and weight are reduced, but the foil becomes prone to curling or wrinkling, making handling and coating difficult
Solution Approach 1:
A protective layer is formed on the surface of the copper foil before it is used in battery assembly. This preliminary protective coating prevents curling and wrinkling during handling and coating operations, making thin foils easier to process without compromising their weight advantage
2Quantity of substance
If a composite active material containing Si or Sn is used to increase charge and discharge capacity, then the battery capacity is improved, but the material rapidly expands due to heat generated during charging or discharging, causing breakage of the electrolytic copper foil
Solution Approach 1:
A protective layer acts as an intermediary between the composite active material and the copper foil. This intermediate layer accommodates the thermal expansion of Si or Sn-containing materials during charging and discharging, preventing direct stress transmission to the copper foil and avoiding breakage while maintaining high capacity
Solution Approach 2:
The protective layer changes its physical parameters (such as flexibility and adhesion) to accommodate thermal expansion during battery operation. This allows the system to handle the rapid expansion of composite active materials without compromising the structural integrity of the copper foil
3Ease of manufacture
If the electrolytic copper foil has high surface smoothness, then the coating process is simplified, but the adhesion with active material is reduced
Solution Approach 1:
The protective layer has different local properties: it provides a smooth surface for easy coating processing while simultaneously providing sufficient adhesion to the active material. This local differentiation of surface properties resolves the contradiction between coating ease and adhesion 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 electrolytic copper foil prevents breakage due to thermal expansion, maintains handleability, and ensures high durability and efficiency of lithium secondary batteries by enhancing adhesion with active materials, reducing wrinkles, and improving charge and discharge capacity retention.
Implementation Method 1
a copper layer by performing electroplating which applies electricity between a positive electrode plate and a rotating negative electrode drum which are disposed to in the electrolytic solution be spaced apart from each other
Implementation Method 2
a coefficient of thermal expansion of the electrolytic foil, which is measured using a thermomechanical analyzer (TMA) while heating the electrolytic copper foil from 30° C. to 190° C.
Data Source
AI summary
An easily handleable electrolytic copper foil securing a highly durable secondary battery, an electrode including same, a secondary battery including same, and a method of manufacturing same. The electrolytic copper foil including first and second surfaces includes a copper layer including a matte surface facing the first surface and a shiny surface facing the second surface, a first protective layer formed on the matte surface of the copper layer, and a second protective layer formed on the shiny surface of the copper layer. A coefficient of thermal expansion of the electrolyte copper foil measured using thermomechanical analyzer while heating the electrolytic copper foil from 30 to 190° C. at 5° C./min ranges from 16 to 22 μm/(m·° C.), tensile strength of the electrolytic copper foil measured after heat treatment at 190° C., ranges from 21 to 36 kgf/mm2, and weight deviation of the electrolytic copper foil is 5% or less.