Positive electrode additive for lithium secondary battery, positive electrode active material comprising same, positive electrode, and lithium secondary battery
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Solution Overview
Problem
Lithium-sulfur secondary batteries face issues with sulfur's non-conductivity and polysulfide elution, leading to poor battery lifetime and rate properties, and existing additives like benzo[ghi]peryleneimide (BPI) dissolve in electrolyte solutions, causing internal short circuits and performance decline.
Innovation Solution
A positive electrode additive represented by Formula 1, where a carbon chain is introduced to benzo[ghi]peryleneimide (BPI), preventing dissolution in electrolyte solutions and enhancing electrochemical activity by being adsorbed onto carbon materials, thereby acting as a catalyst for reactions without inducing internal short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If benzo[ghi]peryleneimide (BPI) is introduced as a positive electrode additive to enhance electrochemical reaction kinetics, then battery performance and lifetime properties are improved, but the additive dissolves in the electrolyte solution causing internal short circuits and performance decline
Solution Approach 1:
The patent modifies the chemical structure of BPI by introducing fluorine atoms at specific positions (positions 2 and 7) of the benzo[ghi]peryleneimide core. This parameter change in molecular structure fundamentally alters the solubility characteristics of the additive, preventing its dissolution in the electrolyte solution while preserving its electrocatalytic activity on the sulfur surface.
Solution Approach 2:
The patent extracts and removes the harmful property (solubility in electrolyte) from the BPI molecule by selectively substituting hydrogen atoms with fluorine atoms at critical positions. This extraction of the problematic characteristic allows the additive to maintain its beneficial electrocatalytic function without causing internal short circuits.
2Use of energy by moving object
If sulfur is used as a positive electrode active material to achieve high energy density, then theoretical energy density reaches 2,800 Wh/kg, but sulfur's non-conductivity and polysulfide elution cause poor battery lifetime and rate properties
Solution Approach 1:
The patent introduces a fluorinated BPI compound as an intermediary substance that mediates between the sulfur active material and the electrolyte. This intermediary acts as a redox mediator and electrocatalyst, facilitating electron transfer and improving reaction kinetics without being consumed in the reaction, thereby enhancing both rate properties and lifetime while preserving high energy density.
Solution Approach 2:
The patent changes the physical and chemical parameters of the sulfur electrode system by introducing the fluorinated additive, which modifies the electrochemical reaction pathways and improves electron conductivity at the sulfur-electrolyte interface, thereby transforming sulfur's poor conductivity into an advantage while maintaining high capacity.
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 additive prevents battery performance decline due to internal short circuits and enhances electrochemical activity, improving the battery's kinetic and lifetime properties by maintaining its presence on the carbon surface without dissolving in the electrolyte.
Implementation Method 1
the BPI acts as a redox mediator, and is capable of enhancing kinetics of an electrochemical reaction
Implementation Method 2
enhancing electrochemical activity by being adsorbed onto carbon materials
Data Source
AI summary
The present disclosure relates to a positive electrode additive for a lithium secondary battery, and a positive electrode active material, a positive electrode and a lithium secondary battery including the same, and in particular, the positive electrode additive represented by Formula 1 is formed on a surface of a carbon material included in the positive electrode active material and is not dissolved in an electrolyte solution, which functions to electrically separate the positive electrode and a negative electrode, and accordingly, battery performance is enhanced by suppressing side reactions in the battery.