Secondary Battery Electrode Composition for Silicon Anode Flexibility
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Solution Overview
Problem
Existing electrode forming compositions using aromatic polyamide-imide (PAI) polymers as binders are limited by their low flexibility, leading to detachment or fractures under mechanical stresses, especially in anodes with silicon-containing electro active materials due to volume changes during charging and discharging, affecting battery efficiency and stability.
Innovation Solution
A new electrode forming composition comprising PAI polymers with specific recurring units and a co-binder material having a low glass transition temperature (Tg) and low enthalpy of fusion, enhancing flexibility and adhesion to current collectors and electro active compounds, particularly in anodes with silicon-based materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If PAI polymers are used as binders in electrode forming compositions, then adhesion to current collector and electro active compounds is improved, but flexibility is reduced leading to detachment or fractures under mechanical stresses
Solution Approach 1:
The patent employs a composite binder system combining PAI polymers with a co-binder material having Tg below 30°C and enthalpy of fusion between 0-90 J/g. This composite approach allows the PAI to provide strong adhesion while the co-binder contributes flexibility and mechanical stress resistance, resolving the contradiction between adhesion strength and flexibility.
Solution Approach 2:
The patent modifies the physical and chemical parameters of the binder system by selecting co-binders with specific thermal properties (Tg < 30°C, ΔHf = 0-90 J/g). These parameter changes enable the binder to maintain adhesion strength while acquiring the necessary flexibility to withstand mechanical stresses during battery manufacturing and operation.
2Quantity of substance
If silicon containing electro active compounds are used in anodes, then lithium concentration and energy capacity are increased, but volume change during charge/discharge causes mechanical stress leading to electrode detachment or fractures
Solution Approach 1:
The patent incorporates a co-binder material with specific thermal properties that acts as a cushioning agent before mechanical stress occurs. The low Tg and controlled enthalpy of fusion of the co-binder allow it to absorb and distribute the mechanical stress generated by silicon volume changes during lithiation/delithiation, preventing electrode detachment and fractures while maintaining high lithium concentration.
3Strength
If electrode forming compositions are made rigid to maintain structural integrity, then mechanical strength is improved, but resistance to volume expansion and contraction is reduced
Solution Approach 1:
The patent creates a composite binder system where PAI polymers provide mechanical strength and structural integrity, while the co-binder material with Tg < 30°C and ΔHf = 0-90 J/g provides flexibility and resistance to volume expansion/contraction. This composite structure allows the electrode to maintain both mechanical strength and adaptability to volume changes during battery operation.
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 composition provides improved mechanical stress resistance and maintains strong adhesion to current collectors and electro active materials, even under volume changes, resulting in stable and efficient electrodes for secondary batteries.
Implementation Method 1
one or more co-binder materials, being selected among polymers having a Tg below 30° C. and having an enthalpy of fusion from 0 to 90 J/g
Data Source
AI summary
The present invention pertains to an electrode-forming composition comprising one or more aromatic polyamide-imide polymers (PAI), one or more electro-active compounds, one or more solvents and one or more co-binder materials being selected among polymers having a Tg below 30° C. and having an enthalpy of fusion from 0 to 90 J/g. The present invention also relates to the use of said electrode-forming composition in a process for the manufacture of an electrode, to said electrode and to an electrochemical device such as a secondary battery comprising said electrode.