Wound Secondary Battery Cathode Loading Asymmetry Against Lithium Plating
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Solution Overview
Problem
Lithium precipitation during charging and discharging reduces the long-term durability of secondary batteries, necessitating improved stability and reliability.
Innovation Solution
A secondary battery design with a specific cathode structure and loading amount gap defined by Equation 1, where the first cathode active material layer is positioned closer to the winding core, and the loading amount gap is adjusted within a certain range to prevent lithium precipitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cathode active material layers are made asymmetric with different loading amounts, then lithium precipitation is prevented and cycle life is improved, but the device complexity increases due to the specific structural requirements and equations
Solution Approach 1:
The patent applies asymmetry by configuring the cathode with two active material layers having different loading amounts (LW1 and LW2) on opposite surfaces of the current collector. This asymmetric structure creates a controlled loading amount gap that prevents lithium precipitation during charging cycles, thereby extending battery cycle life while managing the increased structural complexity through defined geometric relationships.
Solution Approach 2:
The patent utilizes parameter changes by establishing specific relationships between the loading amounts of the two cathode active material layers and the winding core diameter through Equation 1. By adjusting these parameters (LW1, LW2, and X) within defined ranges, the invention optimizes lithium ion distribution and prevents precipitation, improving reliability while maintaining manufacturability.
2Reliability
If the first cathode active material layer is positioned closer to the winding core, then capacity retention is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by positioning the first cathode active material layer closer to the winding core than the second layer. This creates a non-uniform distribution of active material throughout the electrode assembly, with higher concentration near the core where lithium ion transport paths are shorter. This local optimization improves overall capacity retention while the defined geometric relationships provide clear manufacturing guidance.
Data Source
AI summary
A secondary battery according to embodiments of the present disclosure comprises an electrode assembly, which comprises a cathode, an anode disposed opposite to the cathode, and a separation membrane disposed between the cathode and the anode, which is wound around a winding core. The cathode comprises a cathode current collector having a first surface and a second surface that face each other, a first cathode active material layer disposed on the first surface, and a second cathode active material layer disposed on the second surface. A loading amount gap between the first cathode active material layer and the second cathode active material layer, and a diameter of the winding core satisfy a predetermined relationship.