Two-Layer Cathode Structure for Thermal-Stable High-Ni Batteries
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Solution Overview
Problem
Secondary batteries with high-content nickel (High-Ni) NCM positive electrode active materials face stability issues and are prone to exothermic reactions due to internal short circuits, compromising their performance.
Innovation Solution
A positive electrode for lithium secondary batteries is designed with a two-layer structure, where the lower layer has a higher conductive material content (0.5-0.95 wt%) and the upper layer has a lower content (0.05-0.15 wt%), with controlled thickness ratios and materials like carbon nanotubes, enhancing electrical conductivity while suppressing exothermic reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high-content nickel (High-Ni) NCM positive electrode active material is used to increase energy density, then output characteristics and energy density are improved, but thermal stability deteriorates and the battery becomes vulnerable to exothermic reactions
Solution Approach 1:
The positive electrode active material layer is divided into two distinct layers: a lower layer with higher conductive material content (0.5-0.95 wt%) for maintaining electrical conductivity and output characteristics, and an upper layer with lower conductive material content (0.05-0.15 wt%) for improving thermal stability and preventing exothermic reactions during internal short circuits
Solution Approach 2:
Different regions of the positive electrode are assigned different conductive material contents to fulfill different functions: the lower layer near the current collector has higher conductivity for electron transport, while the upper layer has lower conductivity to reduce heat generation and improve safety during abnormal conditions
2Power
If conductive material content is increased to maintain electrical conductivity, then output characteristics are improved, but exothermic reactions are exacerbated
Solution Approach 1:
The conductive material content is segmented across two layers: the lower layer contains 0.5-0.95 wt% conductive material to ensure adequate electrical conductivity for high output, while the upper layer contains only 0.05-0.15 wt% to minimize heat generation and prevent exothermic reactions during internal short circuits
Solution Approach 2:
The conductive material distribution is optimized locally: higher concentration near the current collector where electrical conductivity is critical for performance, and lower concentration at the outer layer where heat generation must be controlled to prevent thermal runaway
Data Source
AI summary
The present invention relates to a cathode for a lithium secondary battery, a manufacturing method therefor, and a lithium secondary battery comprising the cathode. The cathode for a lithium secondary battery comprises a cathode active material layer formed to contain a very low content of conductive material at the outermost side thereof, whereby the cathode can have high thermal stability when an internal short-circuit of a battery occurs, and can achieve high-power properties when applied to a secondary battery.