Positive electrode for lithium-sulfur secondary battery, and lithium-sulfur secondary battery comprising same
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Solution Overview
Problem
Lithium-sulfur secondary batteries face issues with low electrical conductivity, leaching of lithium polysulfide, and rapid capacity decrease due to volume expansion during charging/discharging, which are not adequately addressed by existing porous carbon materials and metal-organic frameworks.
Innovation Solution
A positive electrode for lithium-sulfur secondary batteries is developed, comprising a sulfur-carbon composite, an electrically conductive material, a binder, and a multivalent metal salt with cations like Mg²⁺ and Al³⁺, anions like OH⁻, CO₃²⁻, NO₃⁻, and SO₄²⁻, to enhance conductivity and inhibit polysulfide leaching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a lithium-sulfur secondary battery uses a conventional positive electrode without a binder, then sulfur loading can be increased, but the electrode structure becomes unstable and sulfur particles detach during charging-discharging cycles
Solution Approach 1:
The patent introduces a porous coating layer as an intermediary between the sulfur particles and the current collector. This coating layer acts as a mediator that holds sulfur particles in place without requiring traditional binders, maintaining electrode structural stability while enabling high sulfur loading. The coating layer's porous structure allows lithium ion transport while physically constraining sulfur particles to prevent detachment during cycling.
2Stability of the object's composition
If a lithium-sulfur secondary battery uses a conventional positive electrode with binder, then electrode structure is maintained, but sulfur loading is limited and volume expansion during lithiation cannot be accommodated
Solution Approach 1:
The patent employs a porous coating layer with controlled porosity to accommodate sulfur particles. The porous structure provides void space that can absorb the volume expansion of sulfur during lithiation without compromising electrode integrity. This allows significantly higher sulfur loading compared to conventional dense electrode structures, as the porous framework flexibly adapts to volume changes while maintaining structural stability.
3Stability of the object's composition
If a lithium-sulfur secondary battery uses a positive electrode with traditional binder, then electrode integrity is maintained, but lithium ion permeability is reduced due to binder blocking pores
Solution Approach 1:
The porous coating layer serves as an intermediary that replaces the traditional binder function while improving lithium ion permeability. Unlike conventional binders that block pores and impede ion transport, the porous coating layer's open structure allows efficient lithium ion diffusion. The coating layer maintains electrode integrity through its porous framework rather than through binder adhesion, enabling both structural stability and high ion permeability simultaneously.
4Quantity of substance
If a lithium-sulfur secondary battery uses high sulfur loading in conventional electrodes, then capacity is increased, but sulfur particles detach and battery reliability decreases
Solution Approach 1:
The porous coating layer provides a three-dimensional framework that physically anchors sulfur particles throughout the electrode structure. This porous architecture prevents sulfur particle detachment during charging-discharging cycles by distributing mechanical stress throughout the framework. The high sulfur loading is maintained reliably because the porous structure accommodates volume changes and prevents particle aggregation or detachment, ensuring consistent battery performance and longevity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed electrode design improves cycle performance by effectively inhibiting polysulfide leaching without significantly increasing electrode weight or reducing conductivity, thus enhancing battery performance.
Implementation Method 1
the porous coating layer may serve as a binder-free framework that can absorb volume expansion of sulfur during lithiation
Implementation Method 2
the porous coating layer may serve as a binder-free framework that can retain sulfur particles within the positive electrode, thereby preventing detachment of the sulfur particles from the current collector
Data Source
Figure 1~2
Figure 3
AI summary
Provided is a positive electrode for a lithium-sulfur secondary battery comprising a positive electrode active material, an electrically conductive material, a binder, and a multivalent metal salt. The multivalent metal salt comprises a cation of a metal selected from a group consisting of metals having 3 to 6 of an effective nuclear charge of outermost electrons in the 3rd and 4th periods. The positive electrode for the lithium-sulfur secondary battery can improve the performance of the lithium-sulfur secondary battery by introducing a multivalent metal salt and thus effectively inhibiting the leaching of lithium polysulfide when applied to the battery while not significantly increasing the weight of the electrode and not significantly lowering the conductivity of the electrode.