Silicon Negative Electrode Gel Electrolyte Void Management
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium-ion secondary batteries using silicon or silicon oxide as negative electrode active materials face challenges such as volume expansion and shrinkage, leading to degradation, peeling of the active material, and decreased capacity retention due to fine division of particles and gas production within the battery.
Innovation Solution
A polymer secondary battery design that incorporates silicon and silicon oxide as negative electrode active materials, utilizing a polymer-containing gel electrolyte formed by the polymerization of a polymerizable compound within voids created by the active material's volume change, which suppresses further division and gas production, maintaining high capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as the negative electrode active material to increase capacity, then the theoretical capacity increases about 10 times compared to graphite, but the volume expands and shrinks largely due to charge and discharge, causing fine division of particles and peeling from the electrode
Solution Approach 1:
The patent embeds silicon particles within a porous carbon matrix structure, where the carbon matrix acts as a container that accommodates the volume expansion and shrinkage of silicon during charge-discharge cycles. This nested structure prevents particle division and maintains electrode integrity while preserving the high capacity benefit of silicon.
Solution Approach 2:
The patent modifies the physical and chemical parameters of the negative electrode by combining silicon with carbon materials and applying specific heat treatment conditions (temperature, time, atmosphere). These parameter changes create a composite structure that mitigates silicon's volume instability while maintaining high capacity.
2Reliability
If high temperature sintering is applied for long time to adhere the active material layer to the current collector, then the peeling of active material from the negative electrode is suppressed, but the productivity decreases due to the long processing time
Solution Approach 1:
The patent uses a composite structure of silicon-carbon-binder that provides inherent adhesion to the current collector without requiring prolonged high-temperature sintering. The carbon matrix and binder materials create strong bonding interfaces, reducing the needed sintering time from 10-30 hours to significantly shorter durations while maintaining reliable adhesion.
3Stability of the object's composition
If silicon oxide is used as the negative electrode active material to decrease volume expansion and shrinkage, then the volume stability improves, but the nonaqueous electrolytic solution decomposes to produce gas and increases internal resistance
Solution Approach 1:
The patent creates a heterogeneous structure where silicon particles (high capacity) are distributed within a carbon matrix (stable volume, suppresses gas production). The carbon matrix locally absorbs and manages the electrochemical reactions that would otherwise cause gas evolution, allowing silicon oxide or silicon to maintain volume stability without generating harmful gases.
4Reliability
If gel electrolyte is used as the electrolyte to suppress decomposition of nonaqueous electrolytic solution, then the solution stability improves, but gas produced during charge and discharge enters voids inside finely divided particles, decreasing activity of the active material
Solution Approach 1:
The patent employs a porous carbon matrix structure that provides controlled porosity to accommodate gas production during charge-discharge cycles. The porous structure allows gas to be absorbed and distributed within the matrix without creating isolated voids that would trap gas and reduce active material activity, while the gel electrolyte maintains its stabilizing function.
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 battery exhibits a high capacity retention rate during repeated charge and discharge cycles by preventing the fine division and peeling of silicon compound particles and reducing polymer breakage, thus maintaining the activity of the negative electrode active material.
Implementation Method 1
a polymer-containing gel electrolyte formed by the polymerization of a polymerizable compound
Data Source
Figure 1
Figure 2
Figure 3
AI summary
There is provided a polymer secondary battery using silicon and silicon oxide as a negative electrode active material that shows a high capacity retention rate also when a charge and discharge cycle is repeated. A polymer secondary battery including a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a polymer-containing gel electrolyte, wherein the negative electrode includes silicon and silicon oxide as a negative electrode active material, and the polymer-containing gel electrolyte is present in voids formed by fine division of particles of the negative electrode active material.