Silicon Negative Electrode Composition for Battery Life and Thermal Stability
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Solution Overview
Problem
Lithium secondary batteries face challenges with low energy density due to graphite-based negative electrodes and poor battery life and thermal stability issues with silicon-based electrodes, which require improvements in both performance and durability.
Innovation Solution
A silicon-based negative electrode material co-doped with iron and aluminum, where specific elemental ratios are maintained to enhance thermal stability and kinetic properties, combined with artificial graphite and single-walled carbon nanotubes, and potentially pre-lithiated with lithium silicate, to improve capacity retention and structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrode material is used to improve energy density, then theoretical capacity increases from 372 mAh/g to 3580 mAh/g, but battery life characteristics deteriorate due to large volume expansion (~400%) during repeated charging and discharging
Solution Approach 1:
The patent applies composite materials by combining silicon-based active material with carbon materials (graphite, amorphous carbon) and metal oxides. This creates a composite structure where silicon provides high capacity while carbon and metal oxide components buffer volume expansion, resolving the contradiction between high theoretical capacity and battery life characteristics
Solution Approach 2:
The patent changes physical and chemical parameters of the silicon-based material through doping with metals (Li, Na, K, Ca, etc.) and controlling particle size distribution. These parameter changes modify the electrochemical properties to reduce volume expansion effects while maintaining high capacity, addressing both the capacity improvement and reliability preservation
2Quantity of substance
If silicon-based negative electrode material is used to improve energy density, then theoretical capacity increases to 3580 mAh/g, but thermal stability deteriorates and further improvements are needed
Solution Approach 1:
The patent combines silicon-based material with thermally stable carbon materials and metal oxides to create a composite structure. The carbon and metal oxide components provide thermal stability while silicon maintains high capacity, resolving the contradiction between improved energy density and maintained thermal stability
Solution Approach 2:
The patent applies local quality by creating distinct regions within the electrode structure - silicon-rich regions for high capacity and carbon/metal oxide-rich regions for thermal stability. This spatial differentiation allows each material to perform its optimal function, addressing both capacity and thermal stability requirements
3Stability of the object's composition
If graphite-based negative electrode material is used, then thermal stability and structural integrity are maintained, but energy density decreases due to low theoretical capacity of 372 mAh/g
Solution Approach 1:
The patent creates a composite negative electrode combining graphite (providing thermal stability and structural integrity) with silicon-based material (providing high capacity). This composite structure resolves the contradiction by allowing both materials to contribute their advantageous properties simultaneously
Solution Approach 2:
The patent merges graphite and silicon-based materials into a unified electrode structure where both components work together. The graphite provides stable framework and thermal stability while silicon provides high capacity, achieving both thermal stability and high energy density through merging
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 negative electrode active material including iron and aluminum, wherein in ICP analysis of a negative electrode active material layer including the silicon-based negative electrode active material, contents of elements in the negative electrode active material layer satisfy the following Relations (1) to (3): A/B2+C2≤4,500 5≤B≤1,500 3≤C≤1,000 wherein A is a Li content in ppm, B is an Fe content in ppm, and C is an Al content in ppm, based on the total weight of the ICP-analyzed negative electrode active material layer.