Silicon Negative Electrode Sintering with CO2 Electrolyte
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Solution Overview
Problem
Rechargeable lithium batteries using silicon or silicon alloy as negative electrodes face issues with porosity increase and thickness expansion during charge-discharge cycles, leading to reduced volumetric energy density and cycle performance.
Innovation Solution
Incorporating carbon dioxide into the nonaqueous electrolyte and sintering a mixture of silicon or silicon alloy active material particles with a binder on a conductive metal foil current collector, which forms a stable lithium-ion conducting film, thereby suppressing porosity increase and enhancing adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silicon or silicon alloy particles are used as negative electrode active material, then high charge-discharge capacity is achieved, but porosity increases and thickness expands during charge-discharge cycles
Solution Approach 1:
The patent applies parameter changes by dissolving carbon dioxide in the nonaqueous electrolyte to alter its chemical composition. This modification changes the electrolyte's interaction with the silicon particles, suppressing porosity increase during charge-discharge cycles and preventing excessive thickness expansion while maintaining high charge-discharge capacity
Solution Approach 2:
The patent uses composite materials by combining silicon or silicon alloy particles with a binder to form a composite negative electrode. This composite structure allows the silicon particles to expand and contract during lithium insertion/extraction while the binder maintains structural integrity, preventing particle detachment and electrode disintegration
2Use of energy by moving object
If silicon particles expand and shrink during charge and discharge, then lithium storage and release is achieved, but active material delaminates from current collector
Solution Approach 1:
The patent creates a composite structure where silicon particles are embedded in a binder matrix that is adhered to the current collector. This composite design allows the silicon to undergo volume changes during lithium alloying/dealloying while the binder-current collector composite maintains strong adhesion, preventing delamination and preserving current-collecting capacity
Solution Approach 2:
The patent modifies the electrolyte composition by dissolving carbon dioxide, which changes the chemical environment at the electrode-electrolyte interface. This parameter change enhances the stability of the composite structure during cycling, improving adhesion between the active material layer and current collector
3Use of energy by moving object
If active material particles increase in porosity during cycling, then charge-discharge capacity is maintained, but volumetric energy density decreases
Solution Approach 1:
The patent changes the electrolyte parameter by dissolving carbon dioxide in the nonaqueous electrolyte. This parameter change suppresses the porosity increase of silicon particles during charge-discharge cycling, allowing the electrode to maintain both high charge-discharge capacity and high volumetric energy density by preventing excessive void formation
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 approach improves charge-discharge capacity and cycle performance by reducing electrode thickness and maintaining high volumetric energy density, as evidenced by longer cycle life and reduced porosity in the negative electrode.
Implementation Method 1
a nonaqueous electrolyte containing carbon dioxide dissolved therein
Implementation Method 2
a negative electrode which is a sintered layer of silicon particles and/or silicon alloy particles
Data Source
AI summary
A rechargeable lithium battery including a negative electrode made by sintering, on a surface of a conductive metal foil as a current collector, a layer of a mixture of active material particles containing silicon and/or a silicon alloy and a binder, a positive electrode and a nonaqueous electrolyte, characterized in that the nonaqueous electrolyte contains carbon dioxide dissolved therein.