Graphite-Silicon Anode Composite for Stable Battery Cycle Life
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in maintaining initial cycle-life and long-term cycle-life due to volume changes in non-carbon negative electrode materials like silicon, leading to reduced discharge capacity and increased costs when attempting to address these issues with higher binder and conductive material content.
Innovation Solution
A negative electrode active material composite is developed, comprising artificial graphite primary particles with an amorphous carbon coating and embedded conductive materials, assembled to form secondary particles, which helps in preventing volume changes and improving adhesion, thereby maintaining initial efficiency and long-term cycle-life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If non-carbon negative electrode materials like silicon are used to obtain higher capacity, then the theoretical capacity is improved, but volume changes occur leading to reduced initial cycle-life and long-term cycle-life
Solution Approach 1:
Silicon particles are embedded within artificial graphite particles, creating a core-shell structure where the graphite shell accommodates the volume expansion of the silicon core during lithium insertion, preventing structural degradation and maintaining cycle-life
Solution Approach 2:
An amorphous carbon coating layer is pre-formed on the surface of artificial graphite particles before assembling with silicon particles, providing a protective buffer that prevents direct contact between silicon and electrolyte, reducing side reactions and maintaining initial cycle-life
2Quantity of substance
If non-carbon negative electrode materials like silicon are used to obtain higher capacity, then the theoretical capacity is improved, but long-term cycle-life deteriorates due to volume changes
Solution Approach 1:
The nested structure of silicon particles within artificial graphite particles allows the graphite matrix to accommodate repeated volume changes of silicon during charge-discharge cycles, maintaining structural integrity and ensuring long-term cycle-life
Solution Approach 2:
A composite material system is created combining silicon, artificial graphite, and amorphous carbon coating, where each component serves a specific function: silicon provides high capacity, graphite provides structural stability, and amorphous carbon provides surface protection, collectively achieving both high capacity and long cycle-life
3Reliability
If binder and conductive material content is increased to address volume changes, then cycle-life is improved, but manufacturing cost increases
Solution Approach 1:
The artificial graphite particles themselves serve as both the active material and the structural matrix that accommodates volume changes, eliminating the need for excessive binder materials, while the amorphous carbon coating provides inherent conductivity, reducing the need for additional conductive additives
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 composite achieves a balance in initial discharge capacity, charging rate, and long-term cycle-life while preventing a sharp drop in initial cycle-life, enhancing the performance and durability of rechargeable lithium batteries.
Implementation Method 1
assembling artificial graphite primary particles in the presence of a conductive material and an amorphous carbon precursor, and forming the amorphous carbon coating layer from the amorphous carbon precursor
Data Source
AI summary
A negative electrode active material composite, a method of manufacturing the same, a negative electrode including the same, and a rechargeable lithium battery, the negative electrode active material composite includes secondary particles in which artificial graphite primary particles are assembled; and a conductive material in internal gaps of the secondary particles; wherein at least some of the artificial graphite primary particles include an amorphous carbon coating layer on a surface thereof.