Silicon-Carbon Negative Electrode Structure for Cycle-Stable Capacity
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Solution Overview
Problem
Existing secondary batteries face challenges in achieving high capacity performance and cycle stability due to the large volume expansion of silicon-based negative electrode materials during charging and discharging, which is exacerbated by surface groups that consume active lithium.
Innovation Solution
A secondary battery design incorporating a silicon-carbon composite material with a three-dimensional network cross-linked pore structure and an electrolyte containing specific compounds (formulas I and II) that stabilize active groups, form a robust solid electrolyte interface film, and enhance the mechanical strength of the electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high capacity electrode materials are used to increase battery energy, then the theoretical capacity increases, but the volume expansion during charging and discharging worsens, leading to poor cycle performance
Solution Approach 1:
Silicon particles are nested within the three-dimensional network cross-linked pore structure, allowing the silicon to expand and contract within the confined porous framework during charging and discharging cycles, thereby accommodating volume changes while maintaining structural integrity
Solution Approach 2:
The three-dimensional network cross-linked pore structure acts as a flexible constraint framework that can dynamically adapt to silicon volume changes during lithiation and delithiation, providing mechanical support while allowing necessary expansion and contraction
2Quantity of substance
If silicon content is increased to improve capacity, then the energy density increases, but the volume change during charging and discharging increases, reducing structural stability
Solution Approach 1:
The three-dimensional network cross-linked pore structure provides locally differentiated mechanical properties, with higher density and strength in the pore walls to constrain silicon expansion, while maintaining overall porosity to accommodate volume changes
Solution Approach 2:
The electrode combines silicon particles with a three-dimensional network cross-linked pore structure material to create a composite that leverages the high capacity of silicon while the porous framework provides structural stability and volume change accommodation
3Productivity
If active groups on silicon surface are present to improve reactivity, then the electrochemical activity increases, but active lithium is consumed by these groups, reducing initial coulombic efficiency
Solution Approach 1:
The three-dimensional network cross-linked pore structure serves as an intermediary between the silicon active groups and the electrolyte, moderating their interaction to maintain electrochemical activity while reducing direct consumption of active lithium by surface groups
4Reliability
If the solid electrolyte interface film is formed to protect the electrode, then the electrode protection improves, but the film cracking during silicon expansion reduces cycle performance
Solution Approach 1:
The three-dimensional network cross-linked pore structure enables the solid electrolyte interface film to form a flexible, crack-resistant layer that can accommodate silicon volume changes during charging and discharging, maintaining film integrity and continuous protection throughout cycling
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 initial coulombic efficiency and cycle performance by reducing volume change, stabilizing active groups, and enhancing the structural integrity of the electrode, thereby increasing the battery's capacity and energy density.
Implementation Method 1
the M element of the first component in the electrolyte can be combined with active groups, such as hydroxyl, carboxyl, and amino, on the silicon-carbon composite material, such that the effect of stabilizing active groups is achieved
Implementation Method 2
the first component additive can generate inorganic substances containing M element, such as phosphate and sulfate, in a solid electrolyte film (SEI) on the surface of the silicon-carbon composite material
Implementation Method 3
The silicon-carbon composite material having a three-dimensional network cross-linked pore structure has a stable porous skeleton and good mechanical strength, and can effectively reduce the volume change of silicon before and after charging and discharging
Data Source
AI summary
A secondary battery comprises a negative electrode sheet and an electrolyte; where the negative electrode sheet comprises a silicon-carbon composite material having a three-dimensional network cross-linked pore structure; and the electrolyte contains a first component, the first component containing at least one of compounds represented by formula I and formula II.