Segmented Core Electrode Active Material for Battery Cycle Life
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Solution Overview
Problem
Lithium secondary batteries using metal-based electrode active materials suffer from rapid capacity drop and poor cycle life due to severe volume changes during charge/discharge cycles, despite efforts to enhance capacity with metals like Si and Al.
Innovation Solution
An electrode active material comprising a core layer capable of lithium intercalation/deintercalation, coated with an amorphous carbon layer and a crystalline carbon layer, which inhibits volume variations and maintains conductivity, using a method involving mechanical alloying with crystalline carbon in a Mechano Fusion system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If metal-based electrode active materials (Si, Al) are used to achieve higher charge/discharge capacity, then capacity is improved, but volume changes severely causing cracking and poor cycle life
Solution Approach 1:
The core layer is divided into multiple core particles (at least two) instead of using a single large particle. This segmentation reduces the overall volume change of the core layer during lithium intercalation/deintercalation, preventing cracking and maintaining structural integrity over repeated charge/discharge cycles while preserving high capacity
Solution Approach 2:
The electrode active material is constructed as a composite structure with a core layer containing metal/metalloid core particles and an outer carbon layer. This composite design combines the high capacity of metals with the volume stability of carbon, allowing the metal core to provide high charge/discharge capacity while the carbon layer accommodates volume changes and maintains structural stability for excellent cycle life
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 volume changes
Solution Approach 1:
Dividing the core layer into multiple small core particles reduces individual particle volume changes during lithium intercalation/deintercalation. This segmentation prevents the severe cracking and fragmentation that occurs with single large metal particles, maintaining structural integrity while preserving high overall capacity
Solution Approach 2:
The carbon layer surrounding the core particles acts as a flexible protective shell that can accommodate volume changes of the metal core during charge/discharge cycles. This shell prevents cracking and maintains the structural integrity of the electrode active material, allowing the use of high-capacity metal materials without suffering from their inherent volume expansion problems
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 provides high charge/discharge capacity and excellent cycle life characteristics by stabilizing the core layer's volume and maintaining conductivity, as demonstrated by reduced volume expansion and maintained capacity after multiple charge/discharge cycles.
Implementation Method 1
a core layer capable of repeating lithium intercalation/deintercalation
Implementation Method 2
inhibit variations in volume of the core layer, such as a metal, during repeated charge/discharge cycles
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 in a Mechano Fusion system in the presence of balls
Data Source
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 core layer comprises at least two core particles. A secondary battery comprising the same electrode active material is also disclosed. The electrode active material can inhibit variations in volume of the core layer that may occur during repeated charge/discharge cycles, since the core layer comprising at least two core particles, each core particle having an increased area that is in contact with the carbon layer coated thereon. Therefore, the battery using the electrode active material can provide improved cycle life characteristics.