Multi-Layer Cathode Structure for Stable High-Energy Li-Ion Batteries
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Solution Overview
Problem
Existing lithium secondary batteries face challenges in achieving high energy density while maintaining stability and capacity retention, as increased energy density often leads to reduced stability and capacity retention.
Innovation Solution
A cathode for lithium secondary batteries is designed with a multi-layered structure, where the active material layers nearest to the current collector have a diameter (DA) of 0.5 μm or less, and subsequent layers have varying diameters and lengths (LA) within specific ranges, incorporating different types of cathode active material particles to enhance stability and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium metal oxide is designed to have increased energy density and capacity, then the battery capacity and energy density are improved, but stability and capacity retention are lowered
Solution Approach 1:
The cathode active material layer is divided into multiple sub-layers with different particle size distributions. The first sub-layer contains finer particles (D50: 3-6 μm) while subsequent sub-layers contain progressively coarser particles (D50: 6-12 μm, 12-20 μm). This segmentation allows the battery to achieve high energy density through optimized packing while maintaining stability through the gradual transition in particle sizes that reduces internal stress during charge-discharge cycles.
Solution Approach 2:
Different regions of the cathode active material layer are assigned different particle size characteristics. The lower portion near the current collector has finer particles for better contact and stability, while upper portions have coarser particles for higher energy density. This local differentiation of material properties resolves the contradiction between achieving high capacity and maintaining structural stability.
2Productivity
If lithium metal oxide is designed to have increased power and capacity, then the battery performance is improved, but capacity retention is lowered
Solution Approach 1:
The cathode active material layer is segmented into multiple sub-layers with progressively coarser particle sizes from bottom to top. This segmentation creates optimal conditions for both high charging rates and good capacity retention: finer particles in lower layers ensure good electrical contact and ion transport for high power, while coarser particles in upper layers reduce internal stress and maintain structural integrity for better capacity retention over time.
Solution Approach 2:
The particle size distribution parameter is systematically changed across different sub-layers of the cathode active material layer. By controlling the D50 values to increase from 3-6 μm in the first sub-layer to 12-20 μm in subsequent sub-layers, the invention optimizes both kinetic performance (charging rate) and thermodynamic stability (capacity retention), resolving the contradiction between these two performance metrics.
Data Source
AI summary
A cathode for a lithium secondary battery includes a cathode current collector, and a cathode active material layer including a plurality of active material layers sequentially disposed on the cathode current collector which include different types of cathode active material particles from each other. DA determined by the present disclosure of an active material layer closest to the cathode current collector among the plurality of active material layers is 0.5 μm or less.