Negative Electrode Protrusions for Lithium Battery Cycle Life
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Solution Overview
Problem
Lithium secondary batteries with wound electrode groups face challenges in maintaining cycle characteristics due to heterogeneous charge-discharge reactions and excessive expansion caused by lithium metal deposition, leading to reduced efficiency and lifespan.
Innovation Solution
The battery design incorporates a negative electrode current collector with protrusions on both surfaces, where the area rate of outer-circumference-side protrusions is controlled to be smaller than inner-circumference-side protrusions, reducing stress and surface pressure differences, thereby making the charge-discharge reaction more homogeneous and reducing lithium metal peeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium metal is deposited on the negative electrode during charging, then battery capacity is increased, but heterogeneous charge-discharge reactions occur and cycle characteristics deteriorate
Solution Approach 1:
The patent applies local quality by creating protrusions with different area rates in different regions of the negative electrode current collector. The first region has a first area rate and the second region has a second area rate that is smaller than the first area rate. This spatial variation in protrusion density locally adjusts lithium metal deposition characteristics, making the charge-discharge reaction more homogeneous across different parts of the electrode, thereby improving cycle characteristics while maintaining high capacity.
2Quantity of substance
If lithium metal is deposited on the negative electrode, then battery capacity is increased, but excessive expansion occurs leading to reduced efficiency
Solution Approach 1:
The patent uses local quality by varying the protrusion area rates in different regions to locally control lithium metal deposition and expansion. The second region with smaller area rate experiences less expansion compared to the first region, allowing the electrode structure to better accommodate volume changes during charging and discharging cycles, thereby reducing excessive expansion while maintaining capacity.
3Stability of the object's composition
If protrusions are added to the negative electrode current collector, then charge-discharge reaction homogeneity is improved, but device complexity increases
Solution Approach 1:
The patent applies the porous materials principle by creating a protrusion structure on the negative electrode current collector surface. These protrusions form a controlled porous-like topology that increases surface area and provides sites for lithium metal deposition. The structured protrusions in two different regions create a more homogeneous reaction environment without requiring complex additional components, thus improving reaction homogeneity while limiting complexity increase.
4Reliability
If the area rate of protrusions is varied between regions, then lithium metal peeling is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent implements local quality by defining two distinct regions with different protrusion area rates. The first region has a first area rate and the second region has a second area rate smaller than the first. This local variation in protrusion density creates different adhesion characteristics in different regions, reducing lithium metal peeling. While this does require manufacturing precision to control area rates, the binary regional approach simplifies the manufacturing process compared to continuous variation, making the precision requirement more manageable.
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
This design enhances cycle characteristics by reducing lithium metal density differences and surface pressure, leading to improved charge-discharge efficiency and extended battery life.
Implementation Method 1
Lithium metal is deposited on the negative electrode during charging, and the lithium metal is dissolved in the nonaqueous electrolyte during discharging
Implementation Method 2
a nonaqueous electrolyte having lithium-ion conductivity
Data Source
AI summary
A lithium secondary battery comprises an electrode group and a nonaqueous electrolyte having lithium-ion conductivity. A negative electrode current collector has a first surface facing outward of winding of the electrode group and a second surface facing inward of the winding of the electrode group. At least the first surface or the second surface includes a first region and a second region that is closer to an innermost circumference of the winding of the electrode group than the first region. Protrusions include outer-circumference-side protrusions disposed on the first region and inner-circumference-side protrusions disposed on the second region. In at least the first surface or the second surface, a first area rate is smaller than a second area rate.