Porous Lithium Battery Electrodes with Elastic Polymer Binders
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Solution Overview
Problem
Lithium-ion batteries face issues with mechanical degradation of high-capacity anode active materials due to severe expansion and contraction during charge and discharge cycles, leading to pulverization, detachment from the binder, and reduced cycle life, with existing protective coatings being brittle and non-conductive.
Innovation Solution
A porous electrode structure with high-elasticity polymer-coated particles and a polymer binder that maintains structural integrity by allowing controlled volume expansion, using a high-elasticity polymer with recoverable tensile strain and lithium ion conductivity to bond particles and conductive additives, and incorporating additional pores to manage volume changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-capacity anode active materials (such as Si, Sn, Pb, Ge, Sb, or their alloys) are used to increase specific capacity, then the lithium storage capacity is improved, but severe pulverization and detachment occur during charge-discharge cycles due to expansion and contraction
Solution Approach 1:
The patent applies a flexible polymer coating shell around high-capacity anode particles (Si, Sn, Pb, Ge, Sb or their alloys). This flexible shell accommodates the volume expansion and contraction during lithium insertion and extraction, preventing particle pulverization and detachment from the current collector, thereby maintaining structural integrity and extending cycle life while preserving high lithium storage capacity.
Solution Approach 2:
The patent creates a composite structure consisting of high-capacity anode active material particles coated with flexible polymer material. This composite design combines the high lithium storage capacity of materials like Si and Sn with the mechanical flexibility and stability of the polymer coating, resolving the contradiction between capacity and cycle life through material composition optimization.
2Strength
If conventional resin binders (such as PVDF or SBR) are used to bond anode particles, then structural integrity is maintained, but mechanical degradation occurs due to severe expansion and contraction of high-capacity materials
Solution Approach 1:
The patent replaces conventional rigid resin binders with a flexible polymer coating that forms a shell around anode particles. This flexible shell maintains structural integrity during charging and discharging by elastically deforming with volume changes, preventing particle detachment and mechanical degradation, thereby significantly extending battery cycle life.
Solution Approach 2:
The patent changes the mechanical parameters of the binder material by using polymers with high elastic recovery (stretchability of 100-1000%) instead of conventional rigid resins. This parameter change allows the binder to dynamically adapt to volume fluctuations of high-capacity anode materials during cycling, maintaining both structural integrity and long-term reliability.
3Stability of the object's composition
If protective coatings are applied to prevent pulverization, then mechanical stability is improved, but the coatings are brittle and non-conductive, reducing lithium ion conductivity
Solution Approach 1:
The patent employs a flexible polymer shell coating instead of brittle protective coatings. This flexible shell maintains mechanical stability by elastically accommodating volume changes while preserving lithium ion conductivity through its ion-conductive polymer structure, eliminating the trade-off between mechanical stability and ion conductivity.
Solution Approach 2:
The patent changes the physical and chemical parameters of the protective coating by using soft, flexible, ion-conductive polymers instead of hard, brittle, non-conductive materials. This parameter change enables the coating to simultaneously provide mechanical protection and maintain lithium ion transport pathways, resolving the contradiction between stability and conductivity.
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 solution significantly enhances the cycle life and stability of lithium-ion batteries by preventing mechanical degradation and maintaining structural integrity, achieving higher specific capacity and longer cycle life compared to conventional binders.
Implementation Method 1
a coating polymer that coats the anode active material particles and that has a high elasticity (i.e., the coating polymer has a recoverable tensile strain of at least 5% when measured without an additive dispersed in the coating polymer)
Implementation Method 2
a polymer binder that bonds the anode active material particles and the conductive additives together to form the anode
Implementation Method 3
The anode active material has a specific capacity of lithium storage of greater than 372 mAh/g
Data Source
AI summary
Provided is porous anode or cathode electrode for a lithium battery, the porous electrode comprising multiple particles of an electrode active material (with or without a high-elasticity polymer coating deposited thereon), an optional conductive additive, and a high-elasticity polymer binder that bonds the particles and conductive additive together to form the electrode wherein the multiple particles have pores occupying a pore volume faction Vp and the electrode has pores, external to the multiple particles, occupying a volume faction Ve, wherein Ve and Vp are all based on the total electrode volume, not counting the volume of an electrode current collector, and the total pore volume fraction Vt=Vp+Ve is from 10% to 80% in such a manner that the volume expansion of the electrode during battery charge/discharge operations does not exceed 30% (preferably <20%, more preferably <10% and most preferably 0%).