Undulated Carbon-Coated Silicon Anode for Expansion-Stable Li-Ion Cells
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Solution Overview
Problem
Silicon-oxygen anode materials in lithium ion batteries face issues of volume expansion and low lithium intercalation efficiency due to their inherent properties, leading to degradation of the SEI film and reduced diffusion capacity.
Innovation Solution
An anode material with a silicon-based core coated by a layer having a specific undulation, formed through a method involving an organic carbon source and heat treatment, which enhances conductivity and cycling performance by maintaining electronic pathway connections and suppressing irreversible expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-oxygen material is used as anode material to increase capacity, then lithium intercalation capacity is improved, but volume expansion occurs and SEI film is destroyed
Solution Approach 1:
The patent applies nested structure by placing silicon-based material inside a carbon coating layer, forming a core-shell structure where the inner silicon core provides high lithium capacity while the outer carbon shell constrains volume expansion and protects the SEI film, resolving the contradiction between capacity and stability
Solution Approach 2:
The carbon coating layer acts as a flexible shell that can accommodate the volume changes of silicon during lithium intercalation while maintaining structural integrity, preventing SEI film destruction and pole piece expansion
2Quantity of substance
If silicon-oxygen material intercalates lithium to increase capacity, then lithium content increases, but diffusion capacity decreases due to crystalline phase changes
Solution Approach 1:
The patent changes the physical parameters of the coating layer by controlling its thickness (10-500 nm) and undulation (y≥0.1), creating an optimized structure that facilitates lithium ion transport while maintaining high lithium content in the silicon core
Solution Approach 2:
The undulated carbon coating layer creates a porous-like structure with increased surface area and pathways for lithium ion diffusion, improving diffusion capacity while maintaining high lithium content
3Stability of the object's composition
If carbon coating layer is applied to suppress expansion, then volume stability is improved, but conductivity may decrease due to carbon layer resistance
Solution Approach 1:
The patent optimizes the carbon coating parameters including thickness (10-500 nm) and undulation (y≥0.1), creating a thin yet effective coating that provides volume stability while maintaining sufficient electrical conductivity through the carbon layer
4Reliability
If coating layer thickness is increased to improve conductivity, then powder conductivity is improved, but manufacturing complexity increases
Solution Approach 1:
The patent employs self-service principles where the carbon coating is formed through a simple heat treatment process (400-1200°C) that automatically creates the optimal coating structure without requiring complex multi-step coating procedures, achieving both conductivity and manufacturing simplicity
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 significantly improves the lithium intercalation efficiency, rate performance, and cycling stability of the anode material, reducing damage to the SEI and minimizing expansion, while being suitable for large-scale production with a simpler process.
Implementation Method 1
subjecting the precursor to a heat treatment to obtain the anode material
Implementation Method 2
mixing an organic carbon source, a silicon-based material, and an organic solvent to obtain a precursor; and subjecting the precursor to a heat treatment to obtain the anode material
Data Source
AI summary
An anode material, a preparation method thereof, and a lithium ion battery provided. The anode material includes a core of a silicon-based material and a first coating layer coating on at least part of surface of the core of the silicon-based material, where first coating layer has an undulation y of 1≥y≥0.10, and the undulation y of the first coating layer is expressed by Formula (I):y=1-exp (-(Rmax-Rmin)D50×C)(I)where, Rmax is a maximum thickness (nm) of the first coating layer, Rmin is a minimum thickness (nm) of the first coating layer, D50 is a median particle size (μm) of the anode material, and C is a mass ratio (%) of the first coating layer in the anode material. The anode material of the present disclosure has properties of excellent conductivity, cycling performance, and rate performance, and can suppress occurrence of irreversible expansion.