Core-Shell Carbon Coated Electrode Active Material for Secondary Battery
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Solution Overview
Problem
Current lithium secondary battery electrode active materials, such as metal-based ones, suffer from rapid capacity drop and poor cycle life due to volume changes during lithium intercalation/deintercalation, which limits their practical application.
Innovation Solution
An electrode active material comprising a core layer of metals like Si or Al coated with an amorphous carbon layer and a crystalline carbon layer, where the crystalline carbon layer has sheet-like units with their c-axis perpendicular to the core layer, inhibiting volume variations and maintaining conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If metal-based electrode active materials (Si, Al, etc.) are used to achieve higher charge/discharge capacity, then capacity is improved, but volume changes during lithium intercalation/deintercalation cause cracking and rapid capacity drop
Solution Approach 1:
The patent applies nested structure by placing the metal-based core layer (Si, Al, etc.) inside a carbon-containing layer. The core layer contains the high-capacity metal material while the outer carbon layer protects it from volume expansion damage, creating a nested configuration where the inner element is protected by the outer layer.
Solution Approach 2:
The patent creates a composite material structure combining metal-based core layer with carbon-containing layer. This composite structure integrates the high capacity advantage of metals with the structural stability of carbon, allowing the metal core to provide high capacity while the carbon shell provides mechanical stability during volume changes.
2Quantity of substance
If metal-based electrode active materials are used to achieve higher capacity, then capacity is improved, but the materials crack and divide due to severe volume changes
Solution Approach 1:
The carbon-containing layer acts as a flexible shell that can accommodate volume changes of the metal core during lithium intercalation and deintercalation. This shell structure provides mechanical flexibility to absorb expansion and contraction without causing the core material to crack or fragment.
Solution Approach 2:
The carbon-containing layer serves as a pre-formed protective cushion around the metal core layer before volume changes occur. This beforehand cushioning prevents direct mechanical stress from volume expansion, protecting the metal material from cracking and maintaining structural integrity during charge/discharge cycles.
3Reliability
If conventional electrode active materials are used, then structural stability is maintained, but charge/discharge capacity is insufficient
Solution Approach 1:
The patent applies local quality by assigning different functions to different parts of the electrode active material. The inner core layer is designed for high capacity (metal-based), while the outer layer is designed for structural stability (carbon-containing). Each layer has optimized local properties suitable for its specific function.
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
This configuration enhances charge/discharge capacity and cycle life by preventing volume changes and maintaining electrical conductivity, resulting in a more stable and efficient lithium secondary battery.
Implementation Method 1
a core layer capable of repeating lithium intercalation/deintercalation
Implementation Method 2
show a severe change in volume due to lithium intercalation/deintercalation
Implementation Method 3
maintain high conductivity and conduction paths among the electrode active material particles
Implementation Method 4
carrying out mechanical alloying of the mixture obtained in the first step in a Mechano Fusion system in the presence of balls
Implementation Method 5
the mechanical alloying is performed at a compressive stress to sheer stress ratio of 0.5:1 or more
Data Source
Figure 1~2
Figure 3~4
AI summary
Disclosed is an electrode active material comprising: a core layer capable of repeating lithium intercalation/deintercalation; an amorphous carbon layer; and a crystalline carbon layer, successively, wherein the crystalline carbon layer comprises sheet-like carbon layer units, and the c-axis direction of the sheet-like carbon layer units is perpendicular to a tangent direction of the electrode active material particle. A secondary battery comprising the same electrode active material is also disclosed.