Lithium Secondary Battery Electrode Layout for Plating Suppression
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Solution Overview
Problem
Lithium secondary batteries face performance deterioration and reduced lifespan due to lithium ion deposition on the anode active material layer, which is exacerbated by the anode active material layer accommodating only a portion of desorbed lithium ions from the cathode active material layer.
Innovation Solution
The lithium secondary battery design incorporates a cathode active material layer with a central portion and an outer portion having different specific capacities, where the anode active material layer covers the cathode active material layer and includes a margin portion that does not overlap it, effectively suppressing lithium ion deposition by diffusing excess ions into the margin portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the anode active material layer accommodates only a portion of the lithium ions desorbed from the cathode active material layer, then the battery structure is simple, but lithium ions are deposited on the anode surface causing performance deterioration and reduced lifespan
Solution Approach 1:
The cathode active material layer is divided into a central portion and an outer portion with different specific capacities. The central portion has a higher specific capacity than the outer portion, creating distinct functional zones that control lithium ion distribution and prevent deposition on the anode surface.
Solution Approach 2:
Different regions of the cathode active material layer are assigned different specific capacities to achieve local optimization. The outer portion with lower specific capacity acts as a buffer zone to accommodate excess lithium ions, while the central portion with higher specific capacity provides the main energy storage function.
2Reliability
If the anode active material layer entirely covers the cathode active material layer, then manufacturing is simplified, but lithium ion deposition occurs at the overlapping portion causing performance deterioration
Solution Approach 1:
The anode active material layer is divided into an overlapping portion that covers the cathode active material layer and a margin portion that extends beyond it. This segmentation allows different regions to serve different functions: the overlapping portion for lithium ion insertion and the margin portion for accommodating excess ions.
Solution Approach 2:
The anode active material layer extends in the radial direction beyond the cathode active material layer, creating a margin portion that provides additional space for lithium ion accommodation without increasing the axial thickness of the battery structure.
3Reliability
If the outer portion of the cathode active material layer has high specific capacity, then energy density is improved, but lithium ion deposition occurs at the boundary between overlapping and margin portions
Solution Approach 1:
The cathode active material layer is designed with spatially varying specific capacity: the outer portion has lower specific capacity than the central portion. This local quality differentiation ensures that lithium ions are evenly distributed during charging and discharging, preventing deposition at the boundary between the overlapping and margin portions of the anode.
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 the operational stability and reliability of lithium secondary batteries by reducing lithium precipitation on the anode active material layer, thereby extending the battery's lifespan and maintaining energy density.
Implementation Method 1
Insertion and deintercalation of lithium ions are repeated in the cathode active material layer and the anode active material layer, and charging and discharging of the lithium secondary battery may proceed.
Implementation Method 2
If the anode active material layer accommodates only a portion of the lithium ions desorbed from the cathode active material layer, some lithium ions may be deposited on a surface of the anode active material layer.
Implementation Method 3
The anode active material layer covers the cathode active material layer and includes a margin portion that does not overlap it, effectively suppressing lithium ion deposition by diffusing excess ions into the margin portion.
Data Source
AI summary
A lithium secondary battery includes a cathode including a cathode current collector and a cathode active material layer formed on the cathode current collector, and an anode including an anode current collector and an anode active material layer formed on the anode current collector. The anode active material layer has an area larger than that of the cathode active material layer. The cathode active material layer includes a central portion and an outer portion surrounding the central portion, and the outer portion has a specific capacity less than that of the central portion.