Carbon-Coated Silicon Anode Material for Stable Li Doping
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Solution Overview
Problem
Silicon-based negative electrode active materials for lithium secondary batteries face challenges due to high volume expansion/contraction and irreversible capacity, leading to poor phase stability and reduced charge/discharge efficiency, especially when doped with metals, which can react with moisture and damage the carbon layer.
Innovation Solution
A negative electrode active material is developed with silicon-based particles doped with a Li compound, where a carbon layer is formed after uniform Li doping, preventing lithium by-products and maintaining a neutral pH, thus enhancing the stability and efficiency of the battery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal doping is applied to silicon-based oxide to reduce irreversible capacity, then initial efficiency is improved, but carbon layer is damaged and lithium by-products are formed
Solution Approach 1:
The carbon layer is formed on the silicon-based oxide particles before metal doping is performed. This preliminary carbon coating protects the silicon-based oxide during the doping process, preventing carbon layer damage and suppressing lithium by-product formation while still allowing metal atoms to diffuse into the silicon-based oxide structure to improve initial efficiency.
Solution Approach 2:
The carbon layer acts as an intermediary protective barrier between the silicon-based oxide and the external environment during metal doping. It mediates the doping process by allowing metal diffusion while preventing direct contact that would cause damage and by-products, thus resolving the contradiction between improving initial efficiency and preventing harmful effects.
2Reliability
If metal doping is performed on silicon-based oxide, then irreversible capacity is reduced, but pH of slurry increases due to metal oxide formation
Solution Approach 1:
The carbon layer is pre-formed on the silicon-based oxide before metal doping, creating a protective barrier that prevents excessive metal oxide formation during doping. This preliminary protection maintains slurry pH stability while still allowing the doping to reduce irreversible capacity through controlled metal diffusion into the silicon-based oxide structure.
3Quantity of substance
If silicon-based active material is used for negative electrode, then capacity is higher than carbon-based, but volume expansion/contraction is high
Solution Approach 1:
The invention creates a composite structure where silicon-based oxide particles are coated with a carbon layer and doped with metals. The carbon layer provides structural stability and volume control during expansion/contraction, while the silicon-based oxide core provides high capacity. The metal doping further stabilizes the structure, creating a composite material that achieves both high capacity and volume stability.
Solution Approach 2:
The carbon layer acts as a flexible protective shell around the silicon-based oxide particles. This thin film coating accommodates volume expansion and contraction during charging/discharging cycles while maintaining structural integrity, thus resolving the contradiction between high capacity and volume stability.
4Speed
If silicon-based active material is used for negative electrode, then high-speed charge characteristics are excellent, but charge/discharge efficiency is lowered due to poor phase stability
Solution Approach 1:
The composite structure of carbon-coated, metal-doped silicon-based oxide maintains the high-speed charge characteristics of silicon-based materials while the carbon layer and metal doping provide phase stability. This composite approach preserves the excellent charge speed advantage while correcting the efficiency problem caused by poor phase stability.
Solution Approach 2:
Metal doping changes the physical and chemical parameters of the silicon-based oxide, including phase stability, while preserving the high-speed charge characteristics. The metal atoms modify the electronic structure and phase behavior to improve charge/discharge efficiency without sacrificing charge speed.
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 solution improves the discharge capacity, initial efficiency, and lifespan characteristics of lithium secondary batteries by stabilizing the phase and preventing side reactions, while maintaining a neutral pH and minimizing lithium by-products.
Implementation Method 1
a carbon layer which is formed after uniform Li doping
Data Source
AI summary
A negative electrode active material, a negative electrode slurry including the same, a negative electrode including the slurry, a secondary battery including the negative electrode, and a method of manufacturing a negative electrode active material are disclosed. The negative electrode active material includes silicon-containing particles comprising silicon and a Li compound; and a carbon layer on at least a portion of a surface of the silicon-containing particles. Upon X-ray diffraction analysis, a ratio (p2/p1) of a peak intensity (p2) appearing at 18.8° to 19.0° to a peak intensity (p1) appearing at 24.7° to 24.9° is 0.7 or greater. A pH is 7 to 10 when 1 g of the negative electrode active material is dispersed in 100 mL of water at 25° C.