Silicon-Anode Lithium Battery Depth Control for Fast-Charge Life
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Solution Overview
Problem
Lithium secondary batteries using silicon particles as a negative electrode active material face rapid degradation due to volume expansion, leading to poor lifespan characteristics and quick charging performance, despite their higher theoretical capacity compared to carbon-based materials.
Innovation Solution
A lithium secondary battery design incorporating silicon particles as the negative electrode active material, with a positive electrode active material of overlithiated manganese-based oxide, where the Si charge depth is between 30% and 60% and the Si discharge depth is 10% or greater, optimizing the electrode loading amounts and pre-lithiation capacity to enhance lifespan and charging performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrode active material is used to increase theoretical capacity, then capacity characteristics and quick charging performance are improved, but volume expansion occurs during charging causing damage to negative electrode and disconnection of conductive path, resulting in rapid degradation in battery lifespan
Solution Approach 1:
The patent applies parameter changes by precisely controlling the silicon content ratio in the negative electrode active material within a specific range (5-30 wt%) and optimizing the N/P ratio (1.05-1.30). These parameter adjustments balance the theoretical capacity improvement from silicon while mitigating volume expansion damage, thereby achieving both high capacity and long lifespan characteristics.
Solution Approach 2:
The patent employs composite materials by combining silicon-based negative electrode active material with carbon-based materials to create a composite structure. This composite approach allows the battery to achieve 10 times higher theoretical capacity compared to carbon-based materials alone while the carbon component provides structural stability to counteract silicon's volume expansion during charging, thus improving both capacity and lifespan.
2Speed
If silicon-based negative electrode active material is used to improve quick charging performance through high rate of reaction with lithium, then charging speed is enhanced, but volume expansion causes damage to negative electrode structure, leading to rapid degradation in battery performance
Solution Approach 1:
The patent utilizes parameter changes by optimizing the silicon content ratio (5-30 wt%) and N/P ratio (1.05-1.30) to achieve the right balance between charging speed and performance stability. The controlled silicon content enables high rate of reaction with lithium for quick charging while the optimized N/P ratio ensures structural integrity is maintained during volume expansion cycles.
Solution Approach 2:
The patent applies composite materials by integrating silicon-based active material with carbon-based materials in a composite structure. The silicon component provides high reaction rate for quick charging, while the carbon matrix provides mechanical strength and structural stability to withstand volume expansion, ensuring both fast charging performance and long-term battery stability.
3Quantity of substance
If higher silicon content is used to maximize theoretical capacity, then capacity characteristics improve, but volume expansion during charging increases, causing more severe damage to negative electrode and conductive path disconnection
Solution Approach 1:
The patent applies parameter changes by precisely controlling the silicon content ratio within the optimal range of 5-30 wt%. This parameter optimization ensures that sufficient silicon is present to achieve high theoretical capacity (10 times higher than carbon-based materials) while limiting the volume expansion to manageable levels that do not cause severe structural damage or conductive path disconnection.
Solution Approach 2:
The patent employs composite materials by combining silicon-based active material with carbon-based materials in a composite structure. The silicon component contributes high theoretical capacity, while the carbon matrix provides structural stability and accommodates volume expansion. This composite approach allows maximizing capacity characteristics while controlling volume expansion through the synergistic combination of materials.
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 excellent lifespan characteristics, high capacity, and quick charging performance, with the number of cycles to reach 80% life exceeding 400, while maintaining energy density, by controlling the Si charge and discharge depths within specific ranges.
Implementation Method 1
a negative electrode including a negative electrode active material... the negative electrode active material includes silicon particles
Implementation Method 2
the positive electrode active material includes an overlithiated manganese-based oxide represented by Formula 1 below
Implementation Method 3
an electrolyte... the non-aqueous electrolyte is generally composed of a lithium salt and an organic solvent capable of dissolving the lithium salt
Data Source
AI summary
A lithium secondary battery including a negative electrode including a negative electrode active material, a positive electrode including 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 silicon particles, the positive electrode active material includes an overlithiated manganese-based oxide represented by the disclosed Formula 1, a Si charge depth represented by the disclosed Equation 1 is 30% to 60%, and a Si discharge depth represented by the disclosed Equation 2 is 10% or greater.