Multilayered Positive Electrode for Secondary Battery Penetration Resistance
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Solution Overview
Problem
Lithium secondary batteries face limitations in thermal stability and safety due to issues like internal short circuits and ignition when subjected to external pressure, particularly with lithium nickel composite oxides, which have poor thermal stability and high risk of explosion upon penetration.
Innovation Solution
A manufacturing method for a positive electrode involving a multilayered structure with a first positive electrode slurry having a lithium transition metal oxide with a small average particle diameter applied to a current collector, followed by a second slurry with a larger particle diameter material, reducing the elongation percentage of the lower layer and increasing penetration resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium nickel composite oxide is used to achieve high reversible capacity, then battery capacity increases, but thermal stability deteriorates causing safety issues upon penetration
Solution Approach 1:
The positive electrode is divided into multiple layers with different active materials. The first layer contains lithium nickel composite oxide particles (5-15 μm) providing high capacity, while the second layer contains lithium cobalt composite oxide or lithium manganese composite oxide particles providing thermal stability. This segmentation allows each layer to fulfill its specific function without compromising the other.
Solution Approach 2:
Different regions of the positive electrode are assigned different material compositions based on their functional requirements. The first layer near the current collector uses lithium nickel composite oxide for high capacity, while the second layer uses materials with superior thermal stability for safety. This local differentiation optimizes both capacity and safety in their respective zones.
2Power
If lithium cobalt composite oxide is used to achieve high operating voltage and capacity, then battery performance improves, but cost increases and thermal properties deteriorate
Solution Approach 1:
The invention changes the compositional parameters of the positive electrode by combining lithium nickel composite oxide (high capacity, lower cost) with lithium cobalt composite oxide or lithium manganese composite oxide (high voltage, good thermal stability) in specific ratios. This parameter optimization achieves high operating voltage and capacity while controlling cost and improving thermal properties compared to using pure lithium cobalt oxide.
3Reliability
If nickel is substituted with cobalt or manganese to improve thermal stability, then thermal properties improve, but charge and discharge properties and lifespan properties deteriorate
Solution Approach 1:
Rather than uniformly substituting nickel with cobalt or manganese throughout the electrode, the invention segments the electrode into two layers: the first layer retains lithium nickel composite oxide for excellent charge/discharge properties and lifespan, while the second layer uses lithium cobalt composite oxide or lithium manganese composite oxide for thermal stability. This segmentation preserves the advantages of each material without the drawbacks of uniform substitution.
4Device complexity
If a single-layer positive electrode structure is used to simplify manufacturing, then manufacturing complexity decreases, but penetration resistance decreases causing safety issues
Solution Approach 1:
The positive electrode is segmented into two layers with distinct functions. The first layer contains lithium nickel composite oxide particles (5-15 μm) for high capacity, while the second layer contains lithium cobalt composite oxide or lithium manganese composite oxide particles for thermal stability and penetration resistance. This segmentation enhances safety without significantly complicating the manufacturing process.
Solution Approach 2:
The positive electrode uses a composite structure combining two different lithium transition metal oxide-based active materials in separate layers. This composite approach leverages the high capacity of lithium nickel composite oxide and the high penetration resistance and thermal stability of lithium cobalt composite oxide or lithium manganese composite oxide, achieving superior overall performance.
Data Source
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AI summary
Provided is a method for manufacturing a positive electrode for a secondary battery, the method including applying a first positive electrode slurry including a first positive electrode active material on a positive electrode current collector, forming a first positive electrode mixture layer by primarily rolling the current collector applied with the first positive electrode slurry, applying a second positive electrode slurry including a second positive electrode active material on the above-formed first positive electrode mixture layer, and forming a second positive electrode mixture layer on which the first positive electrode mixture layer is laminated by secondarily rolling the first positive electrode mixture layer applied with the second positive electrode slurry. A positive electrode manufactured as described above may greatly reduce the elongation percentage of a lower layer portion of an electrode adjacent to a positive electrode current collector, thereby increasing penetration resistance when a metal body such as a nail penetrates the electrode from the outside. Accordingly, the present invention may provide a positive electrode for a secondary battery, the positive electrode with improved stability capable of preventing the ignition or explosion of a battery due to overcurrent by suppressing the overcurrent, and a secondary battery including the same.