Silicon-Carbon Anode Electrolyte Design for Cycle Stability
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Solution Overview
Problem
Secondary batteries with high-capacity silicon-based materials face poor cycle performance due to volume expansion during charging/discharging, leading to increased internal resistance and reduced dynamic performance.
Innovation Solution
A secondary battery design incorporating a silicon-carbon composite material with a three-dimensional cross-linked pore network structure and an electrolyte solution containing specific compounds (Formula I and II) that form a solid electrolyte interphase film (SEI) to inhibit volume expansion and reduce interphase resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-capacity silicon-based materials are used as negative electrode active material, then energy density is improved, but cycle performance deteriorates due to volume expansion during charging/discharging
Solution Approach 1:
The patent applies porous carbon materials as a coating layer on silicon-based negative electrode active material. The porous structure provides buffering space for volume expansion during lithiation/delithiation cycles, accommodating the expansion and contraction of silicon without causing structural collapse or particle detachment, thereby maintaining good cycle performance while preserving high capacity.
Solution Approach 2:
The patent creates a composite structure where silicon-based active material is combined with carbon-containing materials (such as conductive carbon, graphite, or amorphous carbon). This composite structure leverages the high capacity of silicon and the structural stability and conductivity of carbon, achieving both high energy density and good cycle performance through synergistic effects.
2Quantity of substance
If high-capacity silicon-based materials are used as negative electrode active material, then energy density is improved, but internal resistance increases leading to reduced dynamic performance
Solution Approach 1:
The porous carbon coating layer provides continuous conductive pathways for electron and ion transport. The porous structure facilitates efficient electrolyte penetration and ion diffusion to the silicon surface, reducing interfacial resistance and improving dynamic performance while maintaining high capacity.
Solution Approach 2:
The patent optimizes parameters such as the thickness, porosity, and composition of the carbon coating layer to balance capacity retention and resistance. By controlling these parameters, the coating layer effectively reduces internal resistance without significantly sacrificing the high capacity of silicon-based materials.
3Quantity of substance
If silicon content in negative electrode is increased to improve capacity, then energy density is improved, but structural stability deteriorates due to volume expansion effects
Solution Approach 1:
The porous carbon coating acts as a protective shell that maintains structural integrity during volume expansion. The porous structure allows the silicon core to expand and contract freely while the carbon shell maintains overall structural stability, preventing particle disintegration even at high silicon content.
Solution Approach 2:
The composite structure of silicon core with carbon shell creates a mechanically stable configuration. The carbon component provides structural support and flexibility to accommodate volume changes, enabling high silicon content (up to 90 wt% or more) while maintaining excellent structural stability and reversible capacity.
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 design improves cycle stability and energy density by enhancing ion migration, reducing internal resistance, and maintaining structural integrity of the battery.
Implementation Method 1
facilitate cyclic radical polymerization or ring-opening polymerization of a cyclic structure of the first component, and form a solid electrolyte interphase film (SEI film) on a silicon-based material
Implementation Method 2
facilitate cyclic radical polymerization or ring-opening polymerization of a cyclic structure of the first component, and form a solid electrolyte interphase film (SEI film) on a silicon-based material
Implementation Method 3
The silicon-carbon composite material having the three-dimensional cross-linked pore network structure has a stable porous framework and good mechanical strength, and can have high loading of silicon and effectively reduce volume changes of silicon during charging/discharging
Implementation Method 4
the first component can be effectively intercalated in the pore structure of the silicon-carbon composite material to be in sufficient contact with the silicon-carbon composite material, so that an ion migration rate at an electrode/electrolyte interphase is improved
Data Source
AI summary
A secondary battery includes a negative electrode plate and an electrolyte solution. The negative electrode plate includes a silicon-carbon composite material having a three-dimensional cross-linked pore network structure. The electrolyte solution includes a first component, and the first component includes one or more of compounds represented by Formula (I) and Formula (II) in this disclosure, in which R1, R2, R3, and R4 includes at least one of a hydrogen atom, a fluorine atom, and a fluorine-substituted or fluorine-unsubstituted C1-C4 alkyl group, and Formula (I) includes fluorine element.