Layered Positive Electrode Sheet for Battery Cycling Stability
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Solution Overview
Problem
The direct physical mixing of positive electrode active materials with different energy densities leads to rapid degradation of battery cells due to differences in electrochemical performance, and separate coating of these materials results in inadequate binding between layers.
Innovation Solution
A positive electrode sheet design where a first positive electrode active material layer with high lattice volume shrinkage is arranged between a current collector and a second layer, with a binder content of 0.8 wt % to 1.5 wt %, to enhance binding and reduce particle detachment during cyclic deintercalation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If positive electrode active materials with different energy densities are directly physically mixed to form a positive electrode active material layer, then the manufacturing process is simplified, but the battery cell or battery will be rapidly degraded in the early stage of cycling due to differences in electrochemical performance
Solution Approach 1:
The patent divides the positive electrode active material layer into multiple sub-layers, each containing different positive electrode active materials with different energy densities. This segmentation allows each sub-layer to maintain its electrochemical characteristics while preventing direct contact and rapid degradation between incompatible materials, thus resolving the contradiction between manufacturing simplicity and cycling stability.
Solution Approach 2:
The patent introduces a binder as an intermediary substance between different positive electrode active materials. The binder acts as a mediator that holds the different materials together in a structured arrangement, preventing direct harmful interactions while maintaining electrical connectivity, thereby enabling both simplified manufacturing and improved cycling stability.
2Reliability
If two positive electrode active materials are separately coated to form two independent positive electrode active material layers, then the electrochemical performance of each material is optimized, but the binding effect between different positive electrode active material layers is insufficient
Solution Approach 1:
The patent merges multiple separately coated positive electrode active material layers into a single integrated layer structure. By combining the layers with appropriate binders and controlling the coating process, the patent achieves both optimized electrochemical performance of individual materials and sufficient binding strength between layers, resolving the contradiction between performance optimization and inter-layer binding.
Solution Approach 2:
The patent creates a composite positive electrode active material layer that incorporates different positive electrode active materials with distinct electrochemical properties. The composite structure maintains the advantages of each individual material while the binder system ensures strong inter-layer binding, thus resolving the contradiction between electrochemical performance optimization and binding strength.
3Strength
If the mass percentage of binder in the first positive electrode active material layer is increased to improve binding performance, then the binding effect between the first positive electrode active material layer and the current collector is improved, but the overall energy density and specific capacity of the battery cell or battery are reduced
Solution Approach 1:
The patent optimizes the mass percentage of binder in the first positive electrode active material layer to a specific range (0.8 wt% to 1.5 wt%). This parameter optimization achieves sufficient binding performance between the first layer and the current collector while minimizing the volume occupied by non-active binder material, thus maintaining high energy density and specific capacity.
Solution Approach 2:
The patent applies different binder content strategies to different regions of the positive electrode active material layer. The first layer (in contact with the current collector) contains a controlled amount of binder (0.8 wt% to 1.5 wt%) to ensure adequate binding, while subsequent layers may have different binder characteristics. This local quality differentiation ensures binding performance where needed while preserving energy density in the bulk active material regions.
Data Source
AI summary
A positive electrode sheet, a battery cell, a battery, and an electric device. The positive electrode sheet includes a positive electrode current collector, and a first positive electrode active material layer and a second positive electrode active material layer which are sequentially arranged on the surface of the current collector. The lattice volume shrinkage of a first positive electrode active material is greater than that of a second positive electrode active material, and the mass percentage of a binder in the first positive electrode active material layer is 0.8 wt % to 1.5 wt %.