Negative Active Material Core-Shell Structure for Lithium Battery
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in achieving improved cycle-life characteristics and active material capacity due to limitations in existing negative active materials, particularly in volume expansion and conductivity during charge and discharge cycles.
Innovation Solution
A negative active material for lithium batteries is developed, comprising a core of crystalline carbon with metal nano particles (Si, Sn, In, or Al) and MOx nano particles (0.5 ≤ x ≤ 1.5) coated with an amorphous carbon layer, mixed in specific weight ratios and particle sizes to enhance cycle-life and capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If non-carbon-based negative active materials (such as Si) are used to improve battery stability and capacity, then active material capacity is improved, but volume expansion occurs during charge and discharge cycles
Solution Approach 1:
The patent embeds metal nanoparticles and MOx nanoparticles within a core-shell structure where crystalline carbon forms the core and amorphous carbon forms the shell. This nested structure allows the high-capacity metal nanoparticles to be contained within a volume-stable carbon matrix, preventing volume expansion while maintaining high capacity.
Solution Approach 2:
The patent creates a composite material system combining metal nanoparticles, MOx nanoparticles, crystalline carbon, and amorphous carbon. This composite structure leverages the high capacity of metals, the volume stability of crystalline carbon, and the protective properties of amorphous carbon to simultaneously achieve high capacity and suppress volume expansion.
2Quantity of substance
If metal nanoparticles are used to enhance active material capacity, then capacity retention is improved, but electric conductivity may be reduced
Solution Approach 1:
The patent introduces carbon materials (both crystalline and amorphous) as intermediary substances that mediate between the metal nanoparticles and the electrolyte. The carbon matrix provides efficient electron transport pathways, ensuring high electric conductivity while allowing the metal nanoparticles to maintain their high capacity characteristics.
3Stability of the object's composition
If crystalline carbon core is used to suppress volume expansion, then structural stability is improved, but surface area for lithium intercalation may be reduced
Solution Approach 1:
The patent transitions from relying solely on two-dimensional surface area to utilizing three-dimensional volume for lithium intercalation. The core-shell structure with porous crystalline carbon core provides internal void spaces and tunnels that allow lithium ions to access the metal nanoparticles through the bulk material, not just the surface, effectively increasing the active surface area in three dimensions.
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 cycle-life retention and active material capacity by suppressing volume expansion and enhancing electric conductivity, with the metal and MOx nano particles in a 9:1 to 2:8 weight ratio and a coating layer thickness of 100 nm to 2000 nm, leading to improved battery performance.
Implementation Method 1
various carbon-based materials (such as artificial graphite, natural graphite, and hard carbon) capable of intercalating and deintercalating lithium ions have been used
Implementation Method 2
A coating layer including an amorphous carbon generally surrounds the core surface, the metal nano particle and the MOx nano particle
Implementation Method 3
The core includes crystalline carbon, and the MOx nano particle is disposed on the core surface
Implementation Method 4
Lithium rechargeable batteries have recently drawn attention as power sources for small portable electronic devices
Data Source
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AI summary
A negative active material for a rechargeable lithium battery includes a core including crystalline carbon, a metal nano particle and a MOx nano particle (where x is from 0.5 to 1.5, and M is Si, Sn, In, Al, or a combination thereof) disposed on the core surface, and a coating layer including an amorphous carbon surrounding the core surface, the metal nano particle and the MOx nano particle. A lithium rechargeable battery includes the negative active material.