Recessed Negative Electrode Collector for Lithium Plating Stability
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Solution Overview
Problem
Lithium secondary batteries face challenges in cycle durability due to the expansion of the negative electrode during charging, leading to decreased capacity retention and irreversible capacity loss.
Innovation Solution
The use of a current collector sheet with recesses in the negative electrode of lithium secondary batteries, where the recesses are arranged to satisfy specific diameter, center-to-center distance, and depth relationships, increases the number of lithium metal deposition origins, reducing current density and suppressing deposit fall-off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium metal is deposited from multiple origins on the negative electrode, then the energy density increases, but the negative electrode expansion increases causing decreased capacity retention rate
Solution Approach 1:
The current collector sheet is segmented into multiple recesses that serve as independent deposition origins. Each recess confines lithium metal deposition to a localized region, preventing uncontrolled expansion across the entire electrode surface. This segmentation allows multiple deposition sites while maintaining overall structural stability and capacity retention.
Solution Approach 2:
The recesses create local regions with different properties from the surrounding current collector surface. The recessed areas provide confined spaces that guide lithium deposition in a controlled manner, creating high-density local deposits while preventing harmful expansion. The local geometric structure modifies the deposition behavior to achieve both high energy density and good capacity retention.
2Reliability
If the number of deposition origins increases, then the current density of each deposit decreases, but the complexity of the current collector structure increases
Solution Approach 1:
The current collector sheet is designed with a porous-like structure consisting of multiple recesses. This approach increases the number of deposition origins without requiring complex surface treatments or coatings. The recessed geometry naturally provides multiple nucleation sites for lithium deposition, achieving low current density per deposit through structural design rather than material complexity.
3Reliability
If protrusions are provided on the current collector to control lithium deposition, then the deposition is controlled, but the manufacturing process becomes complicated
Solution Approach 1:
Instead of adding protrusions that extend outward from the current collector surface, the invention uses recesses that indent into the surface. This inverted approach achieves the same deposition control function while being simpler to manufacture. The recesses can be formed through conventional processes like embossing or molding, avoiding the complexity of attaching separate protrusion elements or performing multi-step surface modifications.
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 configuration improves the cycle durability of lithium secondary batteries by allowing lithium metal to deposit at a high density from multiple origins, reducing expansion of the negative electrode and minimizing irreversible capacity loss.
Implementation Method 1
In a negative electrode of a lithium secondary battery, a dissolution deposition reaction is used. That is, during charging, lithium metal is deposited from the electrolytic solution.
Implementation Method 2
During discharging, the lithium metal dissolves in the electrolytic solution.
Data Source
AI summary
The lithium secondary battery includes a positive electrode, a separator, a negative electrode, and an electrolytic solution. The negative electrode includes a current collector sheet. The thickness of the current collector sheet is 10 μm to 20 μm. The current collector sheet has a plurality of recessed portions. In each of the recesses, assuming that a diameter on a surface is a, a center-to-center distance with another recess closest to the recess is b, and a depth is d, and assuming that an average value of the diameter a is A, an average value of the center-to-center distance b is B, an average value of the depth d is D, and a thickness of the current collection sheet is C, the following expressions (1), (2), and (3): 0.05≤A≤0.18 (1), B≤0.18 (2), and D/C≥3/5 (3) are satisfied.