Silicon Negative Electrode Coating for Cycle Life and Ion Transport
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Solution Overview
Problem
Current secondary batteries face challenges in improving cycle characteristics and charge/discharge efficiency, particularly with silicon-based negative electrode active materials that expand and contract during charging and discharging, leading to reduced performance.
Innovation Solution
A negative electrode active material is developed, comprising silicon-containing particles with a (meth)acrylic acid-based polymer and a siloxane compound coating, which reduces active sites with the electrolyte, suppresses reductive decomposition, and enhances ionic conductivity, thereby improving cycle characteristics and charge/discharge efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based materials are used as negative electrode active material to achieve higher capacity, then the battery capacity increases, but the cycle characteristics deteriorate due to expansion and contraction during charging and discharging
Solution Approach 1:
The patent applies nested structure by placing silicon-based active material particles inside a porous coating layer, which is further enclosed by an outer protective layer. This multi-layer nested structure allows the silicon core to expand and contract during charging-discharging cycles while the porous intermediate layer and outer layer accommodate these volume changes, preventing structural degradation and maintaining cycle stability.
Solution Approach 2:
The patent uses composite material structure consisting of silicon-based active material combined with porous coating materials and protective outer layers. This composite structure combines the high capacity advantage of silicon with the structural stability of the coating materials, resolving the contradiction between achieving high capacity and maintaining good cycle characteristics.
2Quantity of substance
If silicon-based materials are used to increase capacity, then energy density improves, but charge and discharge efficiency deteriorates due to reduced ionic conductivity
Solution Approach 1:
The patent employs porous coating materials with controlled pore structures around the silicon-based active material particles. These porous structures provide efficient ion transport pathways, allowing electrolyte penetration and lithium ion diffusion throughout the particle structure. This maintains high ionic conductivity despite the use of silicon-based materials, thereby preserving charge and discharge efficiency while achieving high energy density.
3Reliability
If a coating layer is added to improve cycle characteristics, then reliability improves, but device complexity increases
Solution Approach 1:
The patent applies local quality by providing coating layers specifically at the surface regions of silicon-based active material particles where expansion and contraction occur during cycling. The coating structure is localized to where it is most needed for protection, rather than requiring complex modifications throughout the entire electrode structure. This targeted approach improves cycle characteristics while minimizing overall device complexity.
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 proposed solution effectively improves cycle characteristics and charge/discharge efficiency by reducing the active sites with the electrolyte and enhancing ionic conductivity, leading to better energy density and stability of the battery.
Implementation Method 1
reduces active sites with the electrolyte, suppresses reductive decomposition
Implementation Method 2
enhances ionic conductivity
Data Source
AI summary
The negative electrode active material includes a plurality of first negative electrode active material particles. Each of the first negative electrode active material particles includes a central portion including silicon and a covering portion provided on a surface of the central portion. The covering portion includes a (meth)acrylic acid-based polymer and a compound having a siloxane bond. The (meth)acrylic acid-based polymer includes at least one of poly(meth)acrylate or a derivative of poly(meth)acrylic acid.