Silicon-Anode Secondary Battery N/P Ratio for Expansion Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing lithium secondary batteries using silicon-based active materials face issues with volume expansion during charge/discharge cycles, leading to reduced lifespan and energy density due to the high capacity of silicon-based active materials.
Innovation Solution
The N/P ratio of discharge capacity between the negative and positive electrodes is adjusted to 1.92 to 2.60, minimizing the volume expansion of silicon-based active materials by controlling the discharge capacity of the negative electrode to be larger than that of the positive electrode, thereby reducing the use ratio of silicon-based active material and maintaining optimal capacity and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based active material is used in the negative electrode, then capacity and energy density are improved, but volume expansion occurs during charge/discharge leading to reduced lifespan
Solution Approach 1:
The patent adjusts the N/P ratio parameter to a specific range (1.05 to 1.30) to optimize the balance between capacity utilization and volume expansion control. By changing this critical parameter, the invention achieves both high capacity and improved lifespan without sacrificing the benefits of silicon-based active material
Solution Approach 2:
The patent intentionally designs the negative electrode capacity to be partially excessive relative to the positive electrode (N/P ratio > 1.0), allowing the silicon-based active material to be partially utilized. This partial utilization strategy prevents excessive volume expansion while maintaining high overall capacity, resolving the contradiction between full capacity utilization and lifespan
2Use of energy by moving object
If silicon-based active material is used in the negative electrode, then energy density is improved, but volume expansion causes deterioration in lifespan properties
Solution Approach 1:
The patent optimizes the N/P ratio parameter within a specific range (1.05 to 1.30) to achieve the best balance between energy density and lifespan. This parameter adjustment ensures that the silicon-based active material contributes maximally to energy density while its volume expansion is kept within acceptable limits for maintaining lifespan properties
3Quantity of substance
If the discharge capacity of the negative electrode is increased to utilize silicon-based active material, then capacity is improved, but volume expansion effects are amplified
Solution Approach 1:
The patent deliberately sets the negative electrode discharge capacity to be partially excessive relative to the positive electrode (N/P ratio > 1.0). This allows the silicon-based active material to be partially utilized, achieving high discharge capacity while preventing the amplification of volume expansion effects that would occur with full utilization
Solution Approach 2:
By adjusting the N/P ratio parameter to a specific range, the patent optimizes the discharge capacity of the negative electrode to achieve the right balance between utilizing silicon-based active material capacity and controlling the harmful volume expansion effects
Data Source
AI summary
The present invention provides a secondary battery including a negative electrode having a negative electrode active material layer containing a negative electrode active material, a positive electrode facing the negative electrode and having a positive electrode active material layer containing a positive electrode active material, a separator interposed between the negative electrode and the positive electrode, and an electrolyte, wherein the negative electrode active material includes a silicon-based active material and an N/P ratio calculated by a specific equation is 1.92 to 2.60.