Positive Electrode Additive for Flexible High-Density Li-Ion Cathodes
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Solution Overview
Problem
Lithium ion battery positive electrode plates prepared with traditional PVDF binders are hard and brittle, leading to brittle failure in the winding process and low pellet density, which reduces energy density and causes issues like flatulence and abnormal thickness in cell systems.
Innovation Solution
A positive electrode additive with a structure containing symmetrical polar ester groups connected to branched-chain alkyl structures is used, which improves the flexibility of the electrode plate, reduces the risk of brittle failure, and increases pellet density by weakening the action force between PVDF molecular chains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If PVDF binder is used to prepare positive electrode plate, then the electrode plate has good binding force, but the electrode plate becomes hard and brittle causing failure in winding process
Solution Approach 1:
The patent introduces a specific additive (containing ester groups and long-chain alkyl structures) as an intermediary substance between PVDF binder and active material particles. This additive mediates the interaction by reducing intermolecular forces between PVDF chains, preventing brittle failure while preserving binding force. The additive acts as a molecular-level mediator that modifies the binder's properties without compromising its adhesive function.
Solution Approach 2:
The patent changes the chemical and physical parameters of the binder system by adding specific compounds with ester groups and long-chain alkyl structures (C12-C18). This parameter change modifies the intermolecular forces, glass transition temperature, and flexibility of the PVDF binder, transforming it from a hard and brittle state to a more flexible state that resists cracking during winding.
2Reliability
If residual NMP is increased to solve hardness and brittleness, then the flexibility improves, but flatulence and abnormal thickness occur in cell system
Solution Approach 1:
The patent replaces the conventional approach of using residual NMP (a solvent that causes harmful effects) with a small amount of specifically designed additive. This additive achieves the flexibility improvement goal without the harmful side effects of NMP residue, effectively substituting a problematic substance with a benign alternative that serves the same functional purpose.
Solution Approach 2:
Instead of relying on residual NMP as an intermediary to provide flexibility, the patent introduces a controlled additive as a new intermediary substance. This additive provides the necessary flexibility through its molecular structure (ester groups and long-chain alkyl structures) without causing the flatulence and thickness abnormalities associated with NMP residue.
3Use of energy by moving object
If adding amount of non-active materials is reduced to obtain higher energy density, then the energy density increases, but electronic conductivity and binding force decrease
Solution Approach 1:
The patent changes the chemical composition parameters of the binder system by incorporating specific additives with ester groups and long-chain alkyl structures. This parameter change allows the binder to maintain adequate binding force with reduced non-active material content, as the additive enhances the binder's effectiveness per unit mass, enabling lower overall binder quantities while preserving binding performance.
4Use of energy by moving object
If adding amount of non-active materials is reduced to obtain higher energy density, then the energy density increases, but electronic conductivity decreases
Solution Approach 1:
The patent modifies the chemical and physical parameters of the binder system through the addition of specific compounds. These parameter changes enhance the binder's conductive properties, allowing reduced non-active material content while maintaining electronic conductivity. The additive's molecular structure facilitates charge transport, compensating for the reduced quantity of conductive materials.
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 use of the positive electrode additive significantly improves the flexibility and pellet density of the electrode plate, enhancing the cycle performance and energy density of lithium ion batteries while maintaining the binding force and reducing the risk of damage during the winding process.
Implementation Method 1
the micromolecular additive can be inserted between the molecular chains of the binder, so that the non-polar long-chain alkyl of the positive electrode additive is clamped between the molecular chains of the binder, the polar C—F bond in the binder is shielded, and the action force between the molecular chains of the binder is reduced
Data Source
AI summary
A positive electrode additive includes a structure shown in Formula I. In Formula I, R1 and R2 are respectively independently selected from C2-C18 alkyls. When the positive electrode additive is applied to the preparation of a positive electrode plate of a lithium ion battery, the flexibility of the electrode plate can be significantly improved, the risk of brittle failure of the electrode plate in the winding process due to the hardness and brittleness can be avoided, and the P.D of the electrode plate can be increased, thereby increasing the energy density of the lithium ion battery.