Silicon Anode Three-Layer Coating for Swelling-Stable Cycling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The swelling and contraction of silicon-based negative electrode materials in lithium-ion batteries during cycling lead to electrode destruction, SEI film growth, and rapid capacity decay, limiting their large-scale application due to high volume changes and poor cycling performance.
Innovation Solution
A three-layer coating structure is applied to silicon-based particles, comprising a carbon layer, a conductive material and organic lithium salt layer, and a polymer layer, which alleviates gas production, reduces electrolyte reactions, and decreases the specific surface area, thereby improving cycling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based particles are used as negative electrode material, then theoretical specific capacity is improved, but volume swelling and cycling performance deteriorate
Solution Approach 1:
The patent applies segmentation by dividing the protective coating into three distinct layers: a first layer containing carbon, a second layer containing conductive material and organic lithium salt, and a third layer containing polymer. This multi-layer structure progressively addresses different aspects of silicon swelling protection, allowing each layer to perform its specific function while collectively improving cycling performance while maintaining high capacity.
Solution Approach 2:
The patent employs composite materials by combining multiple materials with different properties in the coating layers. The first layer uses carbon for basic structural support, the second layer combines conductive material with organic lithium salt for both conductivity and SEI stabilization, and the third layer uses polymer for flexibility and volume change accommodation. This composite approach allows the coating to simultaneously provide mechanical support, electrical conductivity, and chemical stability.
2Quantity of substance
If silicon-based particles are used as negative electrode material, then theoretical specific capacity is improved, but electrode structural stability deteriorates
Solution Approach 1:
The patent applies beforehand cushioning by providing a pre-formed three-layer coating structure on the silicon-based particles before electrode assembly. This coating structure anticipates the volume expansion that will occur during lithium insertion and provides mechanical cushioning to prevent particle fracture. The polymer-containing third layer specifically accommodates volume changes, while the carbon-containing first layer provides structural framework, collectively maintaining electrode structural stability throughout cycling.
Solution Approach 2:
The patent employs flexible shells and thin films through the polymer-containing third layer and carbon-containing first layer, which form flexible protective shells around the silicon particles. These flexible layers can expand and contract with the silicon core during lithiation and delithiation cycles, maintaining structural integrity while accommodating volume changes up to 400%, thereby preventing electrode disintegration.
3Quantity of substance
If silicon-based particles are used as negative electrode material, then theoretical specific capacity is improved, but SEI film stability deteriorates
Solution Approach 1:
The patent applies preliminary action by incorporating organic lithium salt in the second layer and carbon in the first layer that preferentially react with electrolyte to form stable SEI films before the silicon surface is exposed. This preliminary SEI formation prevents direct contact between electrolyte and silicon, avoiding continuous SEI reconstruction and decomposition that would otherwise occur during cycling. The stable SEI film acts as a protective barrier, reducing harmful side reactions and improving overall electrode stability.
Solution Approach 2:
The patent uses intermediary substances by introducing carbon-containing first layer and organic lithium salt-containing second layer as intermediary barriers between the silicon-based particles and the electrolyte. These intermediary layers mediate the interaction between silicon and electrolyte, allowing lithium ion transport while preventing direct harmful reactions. The organic lithium salt specifically acts as an intermediary that forms stable SEI components, reducing electrolyte decomposition and gas production.
4Reliability
If three-layer coating structure is applied to reduce swelling, then cycling performance is improved, but specific surface area decreases
Solution Approach 1:
The patent applies local quality by designing each layer with specific localized functions: the carbon-containing first layer provides structural support close to the silicon surface, the conductive material and organic lithium salt-containing second layer provides conductivity and SEI stabilization at the interface, and the polymer-containing third layer provides flexibility at the outer surface. This localized functional distribution allows the coating to protect the silicon particles effectively while maintaining adequate surface area for lithium ion transport by optimizing each layer's thickness and composition.
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 coating layers enhance the cycling performance and first-cycle charge/discharge efficiency of lithium-ion batteries by reducing volume swelling and stabilizing the SEI film, leading to improved energy density and stability.
Implementation Method 1
performing carbon-coating on the silicon-based particles, to obtain a first intermediate
Implementation Method 2
the second layer contains a first conductive material and an organic lithium salt... reduces electrolyte reactions, and decreases the specific surface area, thereby improving cycling performance
Implementation Method 3
the second layer contains a first conductive material and an organic lithium salt; and the third layer contains a second conductive material and a polymer
Implementation Method 4
the third layer contains a second conductive material and a polymer... alleviates gas production, reduces electrolyte reactions, and decreases the specific surface area
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A negative electrode material includes: a core, where the core includes silicon-based particles; a first layer containing carbon, where the first layer is on an outer side of the core; a second layer containing a first conductive material and an organic lithium salt, where the second layer is on an outer side of the first layer; and a third layer containing a second conductive material and a polymer, where the third layer is on an outer side of the second layer, thereby alleviating volume swelling of the electrochemical apparatus after cycling and improving cycling performance of the electrochemical apparatus.