Electrolytic Copper Foil Residual Stress Control for Battery Cycle Life
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Solution Overview
Problem
Lithium-ion secondary batteries face issues with the cycle life due to cracking and separation of copper foils under expansion and contraction stresses, leading to reduced performance and shorter charge-discharge cycle life.
Innovation Solution
An electrodeposited copper foil with controlled residual stress difference (ΔRS) and void volume (Vv) between its deposited and drum sides, ranging from 0.15 to 1.35 µm³/µm², is developed to enhance adhesion and durability, thereby improving the charge-discharge cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional copper foil is used as current collector, then manufacturing cost is low and electrical conductivity is good, but the copper foil cracks under expansion and contraction stresses during battery cycling
Solution Approach 1:
The patent applies parameter changes by controlling the residual stress difference (ΔRS) between the two surfaces of the copper foil to be 95 MPa or less, and adjusting the void volume (Vv) of the deposited surface to 0.15-1.35 µm³/µm². These parameter optimizations enhance the copper foil's resistance to expansion and contraction stresses during battery cycling, preventing cracks and improving cycle life without changing the fundamental copper material composition.
2Quantity of substance
If high-capacity active substances like silicon, germanium, and tin are mixed with the negative electrode, then battery capacity increases, but expansion and contraction of active substances intensifies and increases stresses on the copper foil
Solution Approach 1:
The patent implements beforehand cushioning by pre-optimizing the copper foil structure before the battery is assembled and used. By controlling the residual stress distribution and void volume on the copper foil surface in advance, the foil is prepared to better withstand the intense expansion and contraction stresses that will occur when high-capacity active substances like silicon, germanium, and tin are used in the negative electrode.
3Productivity
If the copper foil is folded or bent during manufacturing to increase battery capacity, then energy density improves, but the copper foil may crack if it cannot withstand folding and winding
Solution Approach 1:
The patent applies parameter changes by optimizing the residual stress difference (ΔRS) to 95 MPa or less and the void volume (Vv) to 0.15-1.35 µm³/µm². These parameter adjustments enhance the copper foil's flexibility and structural integrity, allowing it to withstand folding and winding operations during battery manufacturing without cracking, thereby enabling higher energy density designs.
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 electrodeposited copper foil significantly extends the charge-discharge cycle life of lithium-ion secondary batteries to 900 times or more by maintaining structural integrity and ensuring effective adhesion of active materials, outperforming conventional copper foils.
Implementation Method 1
anode and a cathode drum, and a copper electrolyte solution, are provided; the copper electrolyte solution is introduced into a space between the anode and the cathode drum; a direct current is applied between the anode and the cathode drum so that copper ions are electrodeposited on the cathode drum
Data Source
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AI summary
Provided are an electrodeposited copper foil, a current collector, an electrode, and a lithium-ion secondary battery comprising the same. The electrodeposited copper foil has a deposited side and a drum side opposite the deposited side. In a first aspect, ΔRS between the deposited side and the drum side is at most about 95 MPa, and the deposited side exhibits a Vv in a range from about 0.15 µm3/µm2 to about 1.35 µm3/µm2. In a second aspect, the deposited side has a Sku of about 1.5 to about 6.5 and the deposited side exhibits a Vv in a range from about 0.15 µm3/µm2 to about 1.35 µm3/µm2. The characteristics are beneficial to improve the quality of the electrodeposited copper foil, thereby extending the charge-discharge cycle life of a lithium-ion secondary battery comprising the same.