Sulfur Grafted Poly(pyridinopyridine) Cathode for Li-Ion Batteries
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Solution Overview
Problem
Lithium ion batteries using sulfurized polyacrylonitrile as cathode active material experience significant decline in discharge capacity and capacity retention with increasing cycles, resulting in low capacity retention after 20 cycles.
Innovation Solution
Development of sulfur grafted poly(pyridinopyridine) (SPPY) with an electrically conductive polymer coating, where sulfur is covalently bonded within a poly(pyridinopyridine) matrix, improving conductivity and cycle stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If sulfurized polyacrylonitrile is used as cathode active material, then initial discharge capacity is high, but capacity retention decreases dramatically with cycling
Solution Approach 1:
The patent uses a composite structure where sulfur is grafted onto the poly(pyridinopyridine) matrix, creating SPPY. This composite material combines the high capacity of sulfur with the structural stability of the PPY matrix, resolving the contradiction between initial capacity and cycle stability. The sulfur atoms are covalently bonded to the matrix, preventing polysulfide dissolution while maintaining electrochemical activity.
Solution Approach 2:
The patent changes the chemical structure parameters by converting polyacrylonitrile into poly(pyridinopyridine) through cyclization reactions. This structural transformation creates a more stable matrix that can better accommodate sulfur and resist degradation during cycling, thereby improving capacity retention while maintaining high discharge capacity.
2Reliability
If sulfur is mixed with polyacrylonitrile and heated to form sulfurized polyacrylonitrile, then conductive and chemically active material is formed, but capacity retention after 20 cycles is only 81.7%
Solution Approach 1:
The patent changes the processing parameters by using controlled cyclization reactions to form poly(pyridinopyridine) instead of simple heating. This creates a more stable polymer matrix with better structural integrity, allowing the material to maintain its chemical activity and conductivity over extended cycling periods, thus extending cycle life.
Solution Approach 2:
The sulfur grafted poly(pyridinopyridine) composite provides both the chemical activity needed for high capacity and the structural stability required for long cycle life. The covalent bonding between sulfur and the PPY matrix prevents material degradation, enabling the battery to maintain performance over hundreds of cycles.
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 SPPY electrode active material maintains high specific capacity and capacity retention, with discharge capacity retention exceeding 95% after 100 cycles, and coulombic efficiencies above 99% over 100 cycles, enhancing lithium ion battery performance.
Implementation Method 1
sulfur is covalently bonded within a poly(pyridinopyridine) matrix
Implementation Method 2
an electrically conductive polymer coated on a surface of the SPPY
Data Source
AI summary
A method for making an electrode active material of a lithium ion battery is provided. A sulfur grafted poly(pyridinopyridine) is synthesized. The sulfur grafted poly(pyridinopyridine) includes a poly(pyridinopyridine) matrix and a plurality of poly-sulfur groups dispersed in the poly(pyridinopyridine) matrix. The electrically conductive polymer is coated on a surface of the sulfur grafted poly(pyridinopyridine). An electrode active material of a lithium ion battery is also provided.