Double-Layer Positive Electrode Plate for Thick Li-Ion Cathodes
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Solution Overview
Problem
Lithium ion batteries face challenges in increasing energy density without compromising electrochemical performance due to severe polarization and poor electrochemical performance caused by thick electrodes, which lead to incomplete reaction of active substances near the current collector and over-reaction near the separator.
Innovation Solution
A positive electrode plate with a double-layer structure comprising a first film layer of hollow particles close to the current collector and a second film layer of solid particles close to the separator, reducing the diffusion path of lithium ions and increasing the specific surface area, thereby enhancing energy density and rate performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If electrode thickness is increased to improve energy density, then the weight proportion of inactive material is reduced, but transmission distance of ions and electrons increases causing severe polarization and poor electrochemical performance
Solution Approach 1:
The electrode is divided into multiple layers with different particle morphologies: a first layer containing hollow particles and a second layer containing solid particles. This segmentation allows each layer to perform different functions - the hollow particle layer provides short diffusion paths and high surface area near the current collector, while the solid particle layer provides high density near the separator, thereby resolving the contradiction between thickness and performance
Solution Approach 2:
Different regions of the electrode are given different particle morphologies tailored to their specific functional requirements. The region near the current collector uses hollow particles for rapid ion transport and high reaction area, while the region near the separator uses solid particles for high compacted density. This local optimization allows the entire electrode to achieve both high energy density and good electrochemical performance
2Quantity of substance
If electrode thickness is increased to reduce inactive material proportion, then energy density improves, but active substance near current collector reacts incompletely and active substance near separator over-reacts
Solution Approach 1:
The electrode is segmented into functional layers with hollow particles in the first layer and solid particles in the second layer. This segmentation creates controlled ion transport pathways that ensure uniform reaction throughout the electrode thickness, preventing both incomplete reaction near the current collector and over-reaction near the separator
Solution Approach 2:
Each layer is designed with specific particle morphology suited to its location: hollow particles near the current collector facilitate complete reaction by providing short diffusion paths and high surface area, while solid particles near the separator prevent over-reaction through their dense structure. This local quality differentiation achieves uniform reaction across the entire electrode
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
The double-layer structure effectively increases the energy density and rate performance of the battery by reducing lithium ion diffusion paths and enhancing the compacted density of the electrode plate, while maintaining electrochemical performance.
Implementation Method 1
reducing the diffusion path of lithium ions (Li+) in the active material
Implementation Method 2
increasing the specific surface area (BET) of the active material, thereby increasing the reaction area of the active material
Data Source
AI summary
A positive electrode plate, a secondary battery comprising the positive electrode plate, as well as a battery module, a battery pack, and a power consuming device are provided. The positive electrode plate of the present invention comprises: a positive current collector and a positive film layer comprising a first positive film layer and a second positive film layer, wherein the first positive film layer is disposed on at least one surface of the positive current collector and comprises a first positive active material comprising a hollow particle material, and the second positive film layer is disposed on the first positive film layer and comprises a second positive active material comprising a solid particle material.