Dual-Film Positive Electrode Plate for Conductivity-Balanced Cycling
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Solution Overview
Problem
Existing lithium-ion batteries face challenges in balancing energy density and reliability due to significant conductivity differences between active materials, leading to electron accumulation and excessive lithium-ion deintercalation, which affects cycling performance.
Innovation Solution
A positive electrode plate design with distinct film layers, one having an olivine or spinel structure and the other a layered structure, with resistivity ratios between 20:1 to 500:1, reducing electron accumulation and enhancing conductivity balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single film layer with high conductivity active material is used, then energy density is improved, but electron accumulation occurs leading to excessive lithium-ion deintercalation and poor cycling performance
Solution Approach 1:
The positive electrode plate is divided into two distinct film layers: a first film layer with high conductivity active material (olivine or spinel structure, R1≤100Ω·cm) and a second film layer with low conductivity active material (layered structure, R2≥1000Ω·cm). This segmentation prevents electron accumulation by providing a conductivity gradient that matches the lithium-ion deintercalation rates of different materials, thereby improving cycling performance while maintaining energy density.
Solution Approach 2:
Different regions of the positive electrode plate are assigned different conductivity characteristics. The first film layer near the current collector provides high conductivity for stable electron collection, while the second film layer further away provides lower conductivity to match the slower lithium-ion deintercalation rate, creating a local quality match between electron transport and lithium-ion transport rates.
2Quantity of substance
If high conductivity active material is used throughout, then energy density is improved, but the difference in conductivity causes electron accumulation on the surface
Solution Approach 1:
The conductivity parameter of the active material is changed across different film layers. The first film layer uses materials with R1≤100Ω·cm (high conductivity) while the second film layer uses materials with R2≥1000Ω·cm (low conductivity), creating a conductivity gradient that prevents electron accumulation by matching electron transport speed with lithium-ion deintercalation speed in each layer.
3Quantity of substance
If mixed active materials are used in a single layer, then energy density is improved, but adhesion between materials causes excessive lithium-ion deintercalation
Solution Approach 1:
Instead of mixing different active materials in a single layer, the patent segments them into two distinct film layers. This physical separation eliminates adhesion issues between incompatible materials while maintaining the energy density benefits of using both high-conductivity (olivine/spinel) and low-conductivity (layered) materials.
Solution Approach 2:
The first film layer acts as an intermediary between the current collector and the second film layer. It provides a high-conductivity interface that facilitates electron collection while the second film layer provides the low-conductivity region that matches the lithium-ion deintercalation rate, mediating the interaction between different material properties.
Data Source
AI summary
A positive electrode plate and a preparation method thereof, a battery cell, a battery, and an electric apparatus are described. The positive electrode plate includes: a positive electrode current collector and a first film layer and a second film layer disposed on the same side of at least one surface of the positive electrode current collector; where the first film layer includes a first active material, and the first active material includes at least one of a material with an olivine structure and a material with a spinel structure; the second film layer includes a second active material, and the second active material includes a material with a layered structure; a resistivity R1 of the first active material and a resistivity R2 of the second active material satisfy: 20≤R2/R1≤500. The technical solution of the embodiment of this application enhances the performance of the battery cell.