Gradient Binder Electrode for Lithium-Ion Battery
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in maintaining the bonding state between active materials and current collectors due to large volumetric changes during charging/discharging, leading to active material pulverization and falling off, which worsens cyclability.
Innovation Solution
A lithium-ion secondary battery electrode design featuring a first electrode layer on the current collector with a higher binder-resin concentration and a second electrode layer with an even higher concentration, disposed to contact the first layer's surface and side faces, to suppress expansion and adhesion enhancement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si or Sn is used as active material to achieve high charging/discharging capacity, then energy density is improved, but volumetric changes cause active material to fall off from current collector
Solution Approach 1:
The binder resin concentration is made non-uniform within the electrode mixture layer, being higher near the current collector and lower toward the outer surface. This local variation in binder concentration provides stronger anchoring at the interface where volumetric expansion occurs, while maintaining porosity and electrolyte access in the bulk active material region.
Solution Approach 2:
The invention changes the concentration parameter of the binder resin within the electrode layer, creating a gradient distribution rather than uniform concentration. This parameter variation allows the electrode to accommodate volumetric changes of Si or Sn active materials while maintaining reliable bonding to the current collector throughout charging/discharging cycles.
2Duration of action of stationary object
If active material particles are pulverized or fall off due to repeated expansion/contraction, then cyclability deteriorates, but using conventional uniform binder distribution fails to suppress this
Solution Approach 1:
The binder resin is concentrated near the current collector interface where the most critical bonding occurs during volumetric expansion. This localized high binder concentration prevents particle detachment at the interface, while the gradual decrease in binder concentration toward the surface maintains adequate porosity for electrolyte penetration and active material flexibility.
Solution Approach 2:
The gradient binder distribution acts as a preventive measure against particle detachment. By having excess binder near the current collector before cycling begins, the structure is pre-configured to accommodate subsequent volumetric expansions and contractions without losing active material particles, thereby cushioning against cyclability deterioration.
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
This configuration effectively inhibits active material from falling off and enhances cyclability by securely bonding the active material to the current collector, improving the battery's capacity and longevity.
Implementation Method 1
a binder resin, an active material and a conductive additive; effectively inhibits active material from falling off and enhances cyclability by securely bonding the active material to the current collector
Implementation Method 2
these materials exhibit large volumetric changes being accompanied by the absorption/release of lithium at the time of charging/discharging
Data Source
AI summary
An electrode for a lithium-ion secondary battery includes a current collector and an electrode layer formed on a surface of the current collector, and including a binder resin, an active material and a conductive additive. The electrode layer includes a first electrode layer and a second electrode layer whose binder-resin concentration is higher than a binder-resin concentration in the first electrode layer. The first electrode layer is disposed on the surface of the current collector and the second electrode layer is disposed on the surface of the current collector at least so as to make contact with the surface of the current collector and at least a side face of the first electrode layer.