Multi-Shell Silicon Anode Particles for Lithium-Ion Batteries
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Solution Overview
Problem
Silicon-based anodes in lithium-ion batteries face degradation due to structural changes during lithiation and delithiation, leading to reduced performance and battery failure, as the expansion and contraction cause cracking, silicon migration, and excessive surface exposure, which increases electrical resistance and consumes electrolyte.
Innovation Solution
The use of multi-shell particles with an amorphous or crystalline silicon-based core coated with a first and second carbon-containing shell, where the second shell has a higher density and carbon content, providing stability and maintaining electrical conductivity while allowing for expansion without fracturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as anode material due to its high theoretical lithium absorption capacity, then the battery capacity is improved, but structural degradation occurs during lithiation/delithiation cycles
Solution Approach 1:
The patent employs a multi-shell nested structure where silicon-based core particles are enclosed within multiple concentric carbon-containing shells. The first carbon-containing shell provides initial protection, while the second carbon-containing shell with higher density and carbon content provides enhanced structural stability. This nested configuration allows the silicon core to expand and contract during lithiation/delithiation without structural degradation, maintaining both high lithium absorption capacity and long-term reliability.
2Quantity of substance
If silicon particles expand during lithium uptake, then lithium absorption capacity is improved, but cracking and fracture occur reducing electrical conductivity
Solution Approach 1:
The patent utilizes flexible carbon-containing shells that can accommodate the volume expansion of silicon particles during lithium uptake. The first carbon-containing shell provides initial flexibility, while the second carbon-containing shell with higher density offers enhanced mechanical strength and electrical conductivity. This flexible shell structure prevents cracking and fracture during expansion/contraction cycles, maintaining continuous electrical conductivity pathways while preserving high lithium absorption capacity.
3Speed
If silicon surface is exposed to electrolyte during cycling, then lithium ion transport is improved, but SEI layer formation consumes excessive electrolyte
Solution Approach 1:
The patent introduces carbon-containing shells as intermediary layers between the silicon core and the electrolyte. These shells act as mediators that facilitate lithium ion transport while preventing direct contact between the silicon surface and electrolyte. The first carbon-containing shell provides initial mediation, while the second carbon-containing shell with higher density and carbon content offers enhanced protection. This intermediary structure maintains fast lithium ion transport kinetics while significantly reducing electrolyte consumption by preventing continuous SEI layer formation on exposed silicon surfaces.
4Stability of the object's composition
If single carbon coating is applied to silicon particles, then structural stability is improved, but electrical conductivity and flexibility cannot be simultaneously optimized
Solution Approach 1:
The patent applies different carbon-containing shell layers with distinct properties at different radial positions around the silicon core. The first carbon-containing shell provides initial structural stability and flexibility, while the second carbon-containing shell with higher density and carbon content provides enhanced electrical conductivity and additional structural support. This local differentiation of shell properties allows simultaneous optimization of structural stability, electrical conductivity, and flexibility, which cannot be achieved with a single uniform carbon coating.
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
This configuration significantly extends the battery's cycle life and capacity retention by preventing structural degradation and maintaining electrical conductivity, reducing the consumption of lithium and electrolyte, thus enhancing the overall performance and longevity of the battery.
Implementation Method 1
Silicon expands by up to 400% during the absorption of lithium, meaning that for each cycle of charging, the silicon will expand during lithium uptake; and then contract through the discharge of the battery during lithium departure
Implementation Method 2
a conductive additive, such as graphite, to provide extra electrical conductivity within the electrode
Data Source
AI summary
Electrical energy storage device (22) comprising an anode (24), a cathode (26) and electrolyte (28), whereby the anode (24) comprises particles (10, 20, 30, 40) comprising an amorphous and/or crystalline silicon-based core (12), a continuous or non-continuous first carbon-containing shell (14, 14a), and a continuous or non-continuous second carbon-containing shell (16, 16a). The second carbon-containing shell (16, 16a) has a higher density and/or a higher atomic percentage of carbon than the first carbon-containing shell (14, 16a).