Silicon Negative Electrode Co-Doping for Battery Life and Thermal Stability
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Solution Overview
Problem
Conventional lithium secondary batteries using carbon-based negative electrode materials have low energy density, and silicon-based alternatives suffer from poor battery life characteristics due to volume expansion and lack of thermal stability.
Innovation Solution
A silicon-based negative electrode material co-doped with iron and aluminum, where the elemental contents satisfy specific ratios, is used to enhance life characteristics and thermal stability, along with the inclusion of artificial graphite and single-walled carbon nanotubes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrode material is used to improve energy density, then capacity increases, but volume expansion occurs during charging and discharging leading to poor battery life
Solution Approach 1:
The patent applies composite materials by combining silicon-based active material with carbon materials (graphite, carbon nanotubes, or carbon fibers) to form a composite negative electrode. This composite structure allows the silicon to provide high capacity while the carbon matrix constrains volume expansion and maintains structural integrity during charging-discharging cycles, thereby extending battery life.
Solution Approach 2:
The patent employs carbon-based shell structures (graphite coating, carbon nanotube networks, or carbon fiber matrices) that act as flexible constraints around the silicon particles. These carbon shells accommodate the volume expansion of silicon during lithiation while preventing particle fragmentation and maintaining electrical conductivity, thus improving both capacity retention and battery lifespan.
2Quantity of substance
If silicon-based negative electrode material is used to improve energy density, then capacity increases, but thermal stability deteriorates
Solution Approach 1:
The patent uses composite materials combining silicon with thermally stable carbon materials (graphite, carbon nanotubes, or carbon fibers). The carbon component provides thermal stability and structural framework that prevents uncontrolled reactions at elevated temperatures, while silicon maintains its high capacity contribution, achieving both high energy density and thermal safety.
Solution Approach 2:
The carbon material acts as an intermediary between silicon particles and the electrolyte/environment. This intermediary layer provides thermal stability and prevents direct exposure of silicon to harsh conditions, thereby improving thermal stability while allowing silicon to function at high capacity.
3Stability of the object's composition
If graphite-based negative electrode is used to ensure stability, then thermal stability is maintained, but energy density decreases
Solution Approach 1:
The patent creates a composite negative electrode combining graphite (providing thermal stability) with silicon-based active material (providing high capacity). The graphite component ensures thermal stability and structural integrity, while the silicon component contributes high theoretical capacity, achieving a balance between stability and energy density that exceeds pure graphite electrodes.
Solution Approach 2:
The patent merges the advantages of graphite (thermal stability, structural integrity) with silicon (high theoretical capacity of 3580 mAh/g) into a single composite electrode system. This merging allows the electrode to simultaneously exhibit thermal stability from graphite and high energy density from silicon, overcoming the limitations of using either material alone.
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 co-doping of iron and aluminum improves the silicon-based negative electrode's thermal stability and kinetic properties, resulting in enhanced capacity retention and uniform voltage distribution, thereby improving the battery's life characteristics and thermal stability.
Implementation Method 1
A silicon-based negative electrode active material co-doped with iron and aluminum
Implementation Method 2
heat treating the product of the process a), thereby preparing a negative electrode active material co-doped with iron and aluminum
Data Source
AI summary
Provided are a negative electrode for a lithium secondary battery and a method of manufacturing the same. The negative electrode for a lithium secondary battery according to an embodiment of the present invention includes a silicon-based material doped with lithium having a content A, iron having a content B, and aluminum having a content C,wherein, by ICP analysis,5,000 ppm≤A≤150,000 ppm,5 ppm≤B≤1,500 ppm,2.5 ppm≤C≤1,000 ppm.