Layered Positive Electrode Plate for Uniform Pre-Lithiation
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Solution Overview
Problem
Lithium-ion batteries face challenges with pre-lithiation technology due to strong alkalinity and large particle size of pre-lithiation agents, leading to non-uniformity, lithium precipitation, and reduced battery performance, as well as contradictions between small particle size active materials causing impurities and side reactions, and large particle size materials reducing power efficiency.
Innovation Solution
A positive electrode plate design with multiple layers, including a capacity layer and a power layer, where the first positive electrode active material has a larger median particle size than the second, and both layers contain specific binders and conductive agents, ensuring uniformity and reducing the adverse effects of pre-lithiation agents, thereby improving power efficiency and cycling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pre-lithiation agents with large particle size are used, then the pre-lithiation layer is easier to form, but the uniformity of the pre-lithiation layer deteriorates
Solution Approach 1:
The positive electrode plate is divided into multiple layers (first positive electrode active material layer, second positive electrode active material layer, third positive electrode active material layer) with different particle size distributions. This segmentation allows each layer to contribute differently to the overall performance, with smaller particles in outer layers for uniformity and larger particles in intermediate layers for ease of formation.
Solution Approach 2:
Different regions of the positive electrode plate have different particle size characteristics. The first and third layers use smaller particle size active materials for uniform pre-lithiation, while the second layer uses larger particle size active materials for ease of formation. This local differentiation resolves the contradiction between uniformity and ease of manufacture.
2Reliability
If pre-lithiation agents with strong alkalinity are used, then the pre-lithiation effect is enhanced, but the risk of lithium precipitation and swelling increases
Solution Approach 1:
The pre-lithiation function is distributed across multiple layers rather than concentrated in a single layer with strong alkalinity. This segmentation reduces the local concentration of alkaline substances, thereby reducing the risk of lithium precipitation and swelling while maintaining the overall pre-lithiation effect.
Solution Approach 2:
The second positive electrode active material layer acts as an intermediary between the first and third layers. This intermediate layer moderates the interaction between the pre-lithiation agents in the outer layers, reducing the harmful effects of strong alkalinity while allowing the pre-lithiation function to occur.
3Quantity of substance
If positive electrode active material with small particle size is used, then the BET specific surface area increases, but the content of entrained impurities and side reactions increases
Solution Approach 1:
The positive electrode plate uses a segmented particle size distribution across different layers. The first and third layers use smaller particle size active materials to provide high BET specific surface area for good electrochemical performance, while the second layer uses larger particle size active materials that have fewer impurities and fewer side reactions.
Solution Approach 2:
Different layers have different particle size qualities suited to their specific functions. The outer layers (first and third) have smaller particles with higher surface area for active electrochemical reactions, while the intermediate layer (second) has larger particles with fewer impurities. This local optimization resolves the contradiction between surface area and impurity content.
4Power
If positive electrode active material with large particle size is used, then the power of batteries increases, but the BET specific surface area decreases
Solution Approach 1:
The positive electrode plate segments the particle size function across layers. The second layer with larger particle size active material provides high power output, while the first and third layers with smaller particle size active material provide high BET specific surface area for good electrochemical activity. This segmentation allows both large and small particle size benefits to coexist.
Solution Approach 2:
Different layers have different particle size qualities optimized for their specific functions. The intermediate layer (second layer) has larger particles optimized for power output, while the outer layers (first and third layers) have smaller particles optimized for surface area and electrochemical activity. This local differentiation resolves the contradiction between power and surface area.
Data Source
AI summary
This application provides a positive electrode plate for lithium-ion battery and a lithium-ion battery containing the same. The positive electrode plate may include a current collector, and a capacity layer and a power layer that are specially designed, able to effectively eliminate, in an economical and simple manner, the adverse impact on the battery performance caused by a product resulting from a pre-lithiation material releasing lithium during charge-discharge cycles, thereby significantly improving the first-cycle coulombic efficiency, cycling performance, and service life of batteries.