Si-C-Graphite Composite Anode for Li-Ion Batteries
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Solution Overview
Problem
Lithium ion secondary batteries using metal anode materials like silicon face challenges due to significant volume expansion during charging, leading to structural breakdown and reduced cycle life, despite improvements with metal-carbon composite particles, as existing solutions do not fully satisfy the requirements for high energy density and long cycle life.
Innovation Solution
A composite anode active material comprising silicon or silicon alloy, carbonaceous material, and graphite, with controlled particle size and shape, specifically a substantially spherical composite particle with a high circularity and optimized composition, is developed to enhance energy density and cycle life by minimizing expansion and maintaining conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If metal materials like silicon are used as anode material to achieve higher capacity, then the theoretical capacity is improved, but the volume increase upon alloying with lithium causes structural breakdown and loss of conductivity
Solution Approach 1:
The patent embeds metal particles (silicon, tin, or other lithium-alloying metals) inside carbonaceous particles, creating a core-shell structure where the metal core provides high lithium storage capacity while the carbon shell maintains structural integrity and conductivity during volume expansion and contraction cycles
Solution Approach 2:
The invention creates composite particles combining metal materials with carbonaceous materials, leveraging the high capacity of metals and the structural stability of carbon to achieve both high energy density and long cycle life
2Reliability
If metal materials are made into fine particles and composite with carbonaceous materials to retain conductivity, then cycle characteristic is improved, but the particle size and shape control becomes more complex
Solution Approach 1:
The patent specifically forms composite particles with spherical or near-spherical shapes, which simplifies packing in electrode manufacturing and improves filling density while maintaining the beneficial effects of fine particle composites for cycle stability
3Duration of action of stationary object
If composite particles are used to improve cycle life, then structural stability is enhanced, but the energy density may be reduced due to lower packing efficiency
Solution Approach 1:
The spherical shape of composite particles enables better packing density in electrode structures, maximizing the amount of active material per unit volume and thereby maintaining high energy density while benefiting from the structural stability of composite design
Solution Approach 2:
The patent optimizes the size parameters of composite particles (controlling diameter and size distribution) to achieve optimal packing efficiency and electrode filling, balancing cycle life improvements with energy density requirements
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 results in an anode with high energy density and excellent cycle characteristics, suppressing reactions with the electrolyte and maintaining initial efficiency through the use of a composite particle structure that maintains bulk density and packing efficiency.
Implementation Method 1
an active material which contains a metal material capable of storing and releasing lithium ions is known to exhibit a significant volume increase upon alloying with lithium by charging
Implementation Method 2
these metal materials create an alloy with lithium, resulting in retention of conductivity due to carbonaceous materials or graphite even when the active material breaks into finer pieces
Implementation Method 3
suppressing reactions with the electrolyte and maintaining initial efficiency through the use of a composite particle structure
Data Source
AI summary
Provided are: an anode active material for a lithium ion secondary battery with which high initial efficiency and battery capacity can be maintained and excellent cycling characteristics are achieved; and a method for producing such an active material. The anode active material for a lithium ion secondary battery, the active material comprising a Si compound and a carbonaceous material or a carbonaceous material and graphite, is obtained by a method comprising the steps of:mixing a Si compound, a carbon precursor, and, as appropriate, graphite powder;performing granulation/compaction;pulverizing the mixture to form composite particles;firing the composite particles in an inert gas atmosphere; andsubjecting the pulverized and conglobated composite powder or the fired powder to air classification.