Low-Expansion Graphite Anode Composition for Silicon Swelling
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Solution Overview
Problem
Existing negative electrode active materials for lithium secondary batteries face challenges in achieving high energy density while minimizing volume expansion, which leads to conductive network disruption and reduced cycle efficiency due to the inclusion of silicon-based materials.
Innovation Solution
A negative electrode active material comprising a carbon-based material, specifically low-expansion artificial graphite, and a silicon-based material, with a balanced composition of 65-95% low-expansion artificial graphite and 1-10% silicon-based material, effectively mitigates volume expansion, maintaining conductive network integrity and enhancing energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional anode materials like graphite or silicon oxide are used, then battery capacity and charging speed can be improved, but dendrite formation occurs during fast charging which reduces battery reliability
Solution Approach 1:
The anode is segmented into multiple layers with different materials: a first anode layer containing graphite or silicon oxide particles, and a second anode layer containing lithium metal powder. This segmentation allows each layer to serve different functions - the first layer provides structural stability while the second layer enables fast charging without dendrite formation
Solution Approach 2:
The patent uses composite materials by combining graphite or silicon oxide with lithium metal powder in a layered structure. The composite anode leverages the advantages of both materials - the stability of graphite/silicon oxide and the high reactivity of lithium metal - while mitigating their individual disadvantages
2Productivity
If lithium metal powder is used in the anode to enable fast charging, then charging speed improves, but the powder may aggregate or disperse unevenly affecting manufacturing precision
Solution Approach 1:
A binder is used as an intermediary substance to uniformly disperse the lithium metal powder within the second anode layer. The binder prevents powder aggregation and ensures uniform distribution, maintaining manufacturing precision while enabling the fast charging capabilities of lithium metal
Solution Approach 2:
The second anode layer is formed as a porous structure with controlled porosity (30-70%) that allows uniform distribution of lithium metal powder while maintaining structural integrity. The porous architecture facilitates even powder dispersion and prevents aggregation during manufacturing and battery operation
3Stability of the object's composition
If the anode contains high porosity to accommodate volume changes, then structural stability improves, but the density of active material decreases reducing battery capacity
Solution Approach 1:
The anode is divided into two functional layers: the first anode layer with lower porosity containing graphite or silicon oxide for high active material density, and the second anode layer with higher porosity containing lithium metal powder for structural stability during fast charging. This segmentation allows optimization of porosity in each layer for its specific function
Solution Approach 2:
The patent optimizes the porosity parameter of the second anode layer to be between 30-70%, balancing structural stability needs with active material density requirements. This parameter optimization ensures sufficient space for volume changes while maintaining adequate lithium content for battery capacity
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 achieves improved cycle characteristics and energy density in lithium secondary batteries, particularly in cylindrical batteries, without requiring modifications to the carbon-based material or silicon-based particles, thus simplifying the manufacturing process and reducing costs.
Implementation Method 1
the second anode layer has a high content of lithium metal powder, the anode may have a fast charge capability
Implementation Method 2
the porous structure may serve to absorb and retain the electrolyte solution
Implementation Method 3
the binder may help to hold the lithium metal powder together
Data Source
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AI summary
The present invention relates to an anode active material for a lithium secondary battery and a secondary battery comprising same and, specifically, to an anode active material comprising low-expansion artificial graphite showing low expansion characteristics upon charge or discharge and a lithium secondary battery comprising same. According to the present invention, an anode active material containing a carbon-based material and a silicon-based material comprises at least a predetermined content of low-expansion artificial graphite, thereby remedying shortcomings of deterioration in energy density and cycle characteristics due to volume expansion, which may occur in an anode active material containing a silicon-based material. Particularly, the present invention achieves a simple manufacturing process and excellent economic feasibility since there is no need to reduce the volume expansion rate of the silicon-based material itself, or to change or process the shape, particle diameter, structure, or the like of the carbon-based material, as in the conventional art.