Stacked Positive Electrode Sheet for Conductivity and Thermal Stability
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Solution Overview
Problem
Lithium-ion battery positive electrodes face issues with poor conductivity, increased polarization during cycling, and safety concerns, particularly in manganese-based and layered oxide materials, leading to reduced cycle life and thermal stability, with existing solutions like carbon-coated aluminum foil being costly and unsuitable for large-scale production.
Innovation Solution
A positive electrode sheet design featuring stacked active material layers, including a manganese-based material and layered oxide material, with specific density, thickness, and mass ratios to enhance conductivity and safety, eliminating the need for carbon-coated aluminum foil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon-coated aluminum foil is used for lithium manganese iron phosphate positive electrodes coating, then electronic conductivity is improved and ohmic impedance is reduced, but production cost increases and large-scale production becomes unsuitable
Solution Approach 1:
The patent replaces expensive carbon-coated aluminum foil with a cost-effective alternative structure: a porous coating layer containing conductive agents (such as acetylene black, super P, or carbon nanotubes) formed directly on the aluminum foil substrate. This coating layer is created through a simple slurry coating process followed by drying and sintering, eliminating the need for expensive pre-coated foils while maintaining good electronic conductivity. The conductive agents in the porous coating provide sufficient conductivity without requiring a carbon coating on the aluminum foil itself.
2Reliability
If lithium manganese iron phosphate and layered oxide materials are mixed to prepare a mixed slurry for coating, then conductivity of lithium manganese iron phosphate is improved and safety of layered oxide materials is enhanced, but coating effects deteriorate and distribution becomes uneven
Solution Approach 1:
The patent divides the electrode structure into distinct functional layers: a first coating layer containing lithium manganese iron phosphate particles and a second coating layer containing layered oxide particles, with the porous coating structure separating these materials. This segmentation prevents direct mixing of the two active materials while maintaining their individual benefits. The porous coating layer acts as an interface that allows ionic and electronic transport between layers without requiring homogeneous mixing, thus achieving both safety enhancement from layered oxide and good coating uniformity.
Solution Approach 2:
The patent applies different material compositions to different layers: the first coating layer near the current collector uses lithium manganese iron phosphate for cost-effectiveness and capacity, while the second coating layer uses layered oxide for safety and thermal stability. The porous coating structure provides local quality by creating distinct zones with different functional properties, allowing each material to perform its optimal function without compromising overall coating uniformity.
3Power
If layered oxide materials are used for positive electrodes, then charge/discharge voltage and specific capacity are improved, but thermal stability decreases and cycling performance deteriorates due to defects like cation mixing and microcracks
Solution Approach 1:
The patent creates a composite electrode structure where layered oxide particles are combined with lithium manganese iron phosphate particles in a porous coating matrix. This composite structure leverages the high specific capacity and voltage of layered oxide while the lithium manganese iron phosphate component and porous structure provide thermal stability and structural support. The porous coating layer with conductive agents also helps reduce microcrack formation by providing a flexible, conductive network that accommodates volume changes during cycling, thereby improving both capacity and thermal stability simultaneously.
Data Source
AI summary
A positive electrode sheet, a method for preparing the positive electrode sheet, and an application of the positive electrode sheet are provided. The positive electrode sheet includes a current collector and an electrode layer arranged on at least one side of the current collector. The electrode layer includes at least a first active material layer and a second active material layer which are arranged in a stacked manner. The first active material layer is in direct contact with a surface of the current collector. An active material in the first active material layer includes a layered oxide positive electrode material, and an active material in the second active material layer includes a manganese-based positive electrode material.