Silicon Anode with Phosphorus-Doped Carbon Shell
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Solution Overview
Problem
Silicon-based anode materials for secondary batteries face challenges with volume expansion during charging and discharging, leading to reduced service life and capacity, despite their high theoretical capacity, due to the formation of a solid electrolyte interface (SEI) layer and dendrite formation when using lithium as the anode material.
Innovation Solution
A silicon-based anode active material is developed with a carbon-based conductive layer and phosphorus doping, where the silicon particles are coated with a silicon oxide shell and doped with phosphorus, which helps in suppressing volume expansion and improving electrical conductivity, thereby enhancing the service life and charging/discharging efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If pure silicon is used as anode material to achieve high theoretical capacity (4,200 mAh/g), then capacity is improved, but volume expansion by about four times during charging causes electrical connection breakage and reduced service life
Solution Approach 1:
The patent employs a core-shell structure where silicon particles (core) are nested within a carbon-coated shell containing phosphorus. This nested configuration allows the high-capacity silicon to be protected by the volume-stable carbon shell, accommodating silicon's volume expansion while maintaining electrical connection and structural integrity throughout charge/discharge cycles.
Solution Approach 2:
The patent creates a composite material system combining silicon, carbon, and phosphorus. The silicon provides high theoretical capacity, the carbon shell provides structural stability and accommodates volume expansion, while phosphorus doping enhances electrical conductivity. This composite approach resolves the contradiction between high capacity and service life by integrating materials with complementary properties.
2Reliability
If SiOx-based composite active material is used to suppress volume expansion and improve service life, then service life is improved, but capacity is reduced and charge/discharge efficiency is deteriorated
Solution Approach 1:
The patent applies local quality by using pure silicon in the core region where high capacity is needed, while applying carbon coating with phosphorus doping on the surface where volume stability and conductivity are needed. This spatial differentiation of material properties allows the interior to maximize capacity while the exterior manages structural stability, avoiding the capacity loss associated with bulk SiOx materials.
Solution Approach 2:
The patent changes the chemical composition parameters by doping phosphorus into the carbon-coated silicon particles. This parameter modification enhances electrical conductivity and facilitates lithium ion transport, thereby improving charge/discharge efficiency and capacity retention without compromising the volume expansion suppression provided by the carbon shell structure.
3Reliability
If carbon-based active material such as graphite is used to ensure stable structure, then service life is improved, but capacity is limited to 372 mAh/g which is insufficient for high capacity battery applications
Solution Approach 1:
The patent merges the advantages of two different material systems: the high capacity of silicon (4,200 mAh/g) and the structural stability of carbon materials. By combining silicon particles with a carbon coating layer, the invention creates a hybrid structure that achieves both high capacity retention and long service life, overcoming the capacity limitation of pure carbon-based anodes while maintaining their structural advantages.
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 silicon-based anode active material exhibits improved capacity retention, high rate performance, and extended service life by minimizing volume changes and maintaining efficient charge/discharge performance, making it suitable for commercialization with a capacity per weight of 1,500 mAh/g and initial charging/discharging rates above 85%.
Implementation Method 1
phosphorus doped in the particles
Implementation Method 2
particles comprising silicon and oxygen combined with the silicon
Implementation Method 3
a carbon-based conductive layer is coated with on outermost surface of the particles
Data Source
AI summary
The present invention relates to a silicon-based anode active material and a method of fabricating the same. The silicon-based anode active material according to an embodiment of the present invention comprises: particles comprising silicon and oxygen combined with the silicon, wherein a carbon-based conductive layer is coated with on outermost surface of the particles; and phosphorus doped in the particles, wherein a content of the phosphorus with respect to a total weight of the particles and the phosphorus doped in the particles have a range of 0.01 wt % to 15 wt %, and a content of the oxygen has a range of 9.5 wt % to 25 wt %.