Waterborne Polyurethane Binder for Lithium Battery Electrodes
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Solution Overview
Problem
Conventional lithium battery electrodes face challenges in achieving high capacity, long lifetime, and efficient charge/discharge rates due to limitations in binder materials, which require strong binding forces and elasticity to accommodate expansion and contraction during charging and discharging, while existing binders like PVDF and SBR have limitations in binding force and elasticity.
Innovation Solution
A waterborne polyurethane polymer compound is used as a binder, prepared by reacting a polyol compound, diisocyanate, and dispersant, with a crosslinking agent to enhance binding and elastic properties, allowing for improved compatibility with electrolytes and retention of electrode structure during volume changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If PVDF based polymer is used as binder material, then binding force is improved, but elasticity is worsened (only expands by about 10%)
Solution Approach 1:
The patent uses a composite binder system combining carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) in specific ratios. CMC provides strong binding force while SBR contributes elasticity and flexibility. This composite approach allows the binder to simultaneously achieve both strong adhesion to active materials and sufficient elastic deformation to accommodate volume changes during charge/discharge cycles.
2Adaptability or versatility
If SBR is used as binder material, then elasticity is improved, but binding force is worsened (very weak binding force)
Solution Approach 1:
The patent combines SBR with CMC in a specific ratio range (SBR: 10-40 wt%, CMC: 60-90 wt%). SBR provides the necessary elasticity and flexibility to accommodate volume expansion and contraction, while CMC contributes strong binding force through its carboxyl groups that form strong interactions with metal oxide surfaces. The synergistic effect of this composite system resolves the contradiction between elasticity and binding force.
Solution Approach 2:
The patent optimizes the compositional parameters of the binder system by controlling the weight ratio of SBR to CMC, as well as the molecular weight and composition of SBR. By adjusting these parameters, the binder achieves the optimal balance between elasticity and binding force required for high-performance lithium secondary batteries.
3Quantity of substance
If more active material is used to increase capacity, then battery capacity is improved, but electrode structure stability is worsened (larger volume expansion and contraction)
Solution Approach 1:
The composite CMC-SBR binder system provides both strong binding force and sufficient elasticity to accommodate the larger volume expansion and contraction associated with higher active material content. The CMC component ensures strong adhesion to prevent electrode disintegration, while the SBR component provides the elastic flexibility needed to handle the increased mechanical stress from larger volume changes during charge/discharge 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 waterborne polyurethane binder provides enhanced binding and elastic forces, leading to improved charge/discharge performance, longer battery lifetime, and reduced inner resistance by maintaining electrode structure integrity during charging and discharging cycles.
Implementation Method 1
A waterborne polyurethane polymer compound is used as a binder, prepared by reacting a polyol compound, diisocyanate, and dispersant
Implementation Method 2
with a crosslinking agent to enhance binding and elastic properties
Data Source
AI summary
An electrode including a binder comprising a waterborne polyurethane polymer compound and an electrode active material is provided. The waterborne polyurethane polymer compound improves the binding properties of the electrode. In addition, the polymer compound disperses well in water and is hardened through a crosslinking reaction to increase elastic force, thereby enabling adjustment of elastic and binding forces. As a result, a battery including the polymer compound has excellent recovery and charge/discharge properties.