Polymer-Coated Silicon-Carbon Anodes for Longer Battery Cycle Life
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Solution Overview
Problem
Existing rechargeable lithium batteries face challenges in achieving high energy density and cycle-life characteristics due to side reactions between the negative active material and electrolyte, particularly when using silicon-based materials.
Innovation Solution
A negative active material is developed with a silicon-carbon composite core coated by a cross-linked polymer layer, which includes a phenol group-included first repeating unit and an amine group-included second repeating unit, forming a polymer coating layer that prevents electrolyte dissolution and enhances lithium ion and electron mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative active materials are used to achieve high capacity and energy density, then the battery capacity increases, but side reactions with electrolyte occur leading to poor cycle-life characteristics
Solution Approach 1:
A polymer coating layer is introduced as an intermediary between the silicon-based negative active material and the electrolyte. This coating layer prevents direct contact and side reactions between the silicon material and electrolyte, thereby improving cycle-life characteristics while maintaining the high capacity benefits of silicon-based materials.
Solution Approach 2:
The negative active material is designed as a composite structure consisting of silicon-based material combined with a polymer coating layer. This composite structure combines the high capacity advantage of silicon with the stability and protective properties of the polymer coating, resolving the contradiction between capacity and cycle-life.
2Reliability
If a coating layer is added to prevent side reactions, then cycle-life characteristics improve, but the device structure becomes more complex
Solution Approach 1:
A thin polymer coating layer is applied on the surface of the silicon-based negative active material. This thin film structure provides protection against side reactions and improves cycle-life characteristics without significantly increasing structural complexity or occupying excessive space.
3Reliability
If a polymer coating layer is formed to suppress side reactions, then cycle-life improves, but lithium ion and electron mobility may be hindered
Solution Approach 1:
The polymer coating layer is designed with specific compositional parameters (ratio of N1s peaks at 400±0.5 eV to 405±0.5 eV of about 1.02 to 1.6, and ratio of C1s peaks at 286.5±0.5 eV to 290±0.5 eV of about 1.02 to 3.0) that optimize both protective function and ion/electron transport properties, balancing cycle-life improvement with maintained mobility.
Solution Approach 2:
The polymer coating layer is designed to have different local properties: it provides dense protection against electrolyte penetration while maintaining regions with adequate conductivity for lithium ion and electron transport. This localized differentiation of properties allows simultaneous achievement of improved cycle-life and maintained mobility.
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 polymer coating layer improves cycle-life characteristics by suppressing side reactions and maintaining efficient lithium ion and electron movement, thereby enhancing the battery's performance and capacity.
Implementation Method 1
a polymer coating layer formed on the core, wherein the negative active material has about 1.02 to about 1.6 of a ratio of height of a N1s peak occurring at about 400±about 0.5 eV relative to a height of a N1s peak occurring at about 405±about 0.5 eV
Implementation Method 2
maintaining efficient lithium ion and electron mobility
Implementation Method 3
maintaining efficient lithium ion and electron mobility
Data Source
AI summary
A negative active material includes a core having a silicon-carbon composite and a polymer coating layer formed on the core, wherein the negative active material has about 1.02 to about 1.6 of a ratio of height of N1s peak occurring at about 400±about 0.5 eV relative to a height of N1s peak occurring at about 405±about 0.5 eV of a bonding energy, and about 1.02 to about 3.0 of a ratio of a height of C1s peak occurring at about 286.5±about 0.5 eV relative to a height of C1s peak occurring at about 290±about 0.5 eV when an X-ray photoelectron spectroscopy (XPS) is measured.