High-Nickel Electrode Sheet Edge Layers for Moisture Stability
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Solution Overview
Problem
Conventional high-nickel positive electrode active materials in lithium secondary batteries suffer from rapid deterioration due to moisture reactivity, leading to decreased capacity and thermal instability, which conventional solutions fail to adequately address.
Innovation Solution
An electrode sheet design with distinct positive electrode mixture layers of varying particle strength and size, where the edges have a stronger positive electrode active material to mitigate moisture reactivity while maintaining high energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the content of nickel in the positive electrode active material is increased to improve energy density, then the energy density per volume increases, but the structural stability and chemical stability of the active material decrease, leading to rapid deterioration of thermal stability and increased reactivity with moisture
Solution Approach 1:
The patent applies local quality by creating a gradient in nickel content across the electrode sheet width. The central portion contains high-nickel positive electrode active material (Ni content: 80-90 mol%) for high energy density, while the edge portions contain low-nickel positive electrode active material (Ni content: 30-50 mol%) for high chemical stability and low moisture reactivity. This spatial variation in composition allows the electrode to simultaneously achieve high overall energy density while maintaining stability at moisture-prone edges.
2Volume of stationary object
If the electrode sheet is stored in a wound state to save space, then storage efficiency improves, but moisture can more easily permeate into the both ends than the central portion, leading to higher moisture content at the edges and increased probability of nickel reaction with moisture
Solution Approach 1:
The patent applies preliminary anti-action by pre-configuring the electrode sheet with enhanced moisture resistance at the edge portions before storage. The low-nickel positive electrode active material is specifically placed at the edges that will be exposed during wound-state storage, creating a protective barrier against moisture permeation before the harmful effect occurs. This preventive structural design counteracts the inherent vulnerability of edge portions in wound storage.
3Reliability
If conventional solutions apply low-nickel material at both ends to suppress lithium precipitation, then lithium precipitation is suppressed, but the nickel content is limited to 20-40% which is insufficient for achieving desired energy density
Solution Approach 1:
The patent applies parameter changes by optimizing the nickel content parameters in the edge portions to 30-50 mol%, which is higher than the conventional 20-40% range. This parameter adjustment maintains sufficient chemical stability to suppress lithium precipitation and reduce moisture reactivity, while simultaneously increasing the nickel content enough to contribute to overall energy density. The central portion maintains high nickel content (80-90 mol%) for maximum energy density.
Data Source
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AI summary
In the present invention, a slurry for a second cathode mixture is applied to both edge regions of an electrode sheet holing portion during storage of an electrode sheet having a high content of nickel, wherein the edge regions are vulnerable to moisture penetration and high in rolling reduction ratio and the slurry contains a cathode active material more resistant to rolling than that applied to the center region of the holding portion, whereby the reactivity of nickel and moisture is suppressed as much as possible to improve the lifespan characteristics of the battery.