Porous Silicon-Carbon Anode Coating for Volume-Stable Li-Ion Capacity
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Solution Overview
Problem
Lithium secondary batteries face challenges with silicon anode materials due to high volume expansion and contraction, leading to pulverization and low electrical conductivity, which existing measures fail to adequately address, and these issues are costly.
Innovation Solution
An anode active material is developed with a porous particle structure containing specific sized spaces, coated with primary, silicon, and secondary carbon layers to accommodate volume changes and enhance conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as anode active material to increase theoretical capacity, then charge capacity is improved, but volume expansion causes pulverization and separation from electrode
Solution Approach 1:
The anode active material is divided into two distinct components: graphite particles (providing structural stability) and silicon particles (providing high capacity). This segmentation allows each material to perform its optimal function while mitigating silicon's volume expansion issues through the graphite matrix
Solution Approach 2:
Silicon particles are nested within or coated on graphite particles, creating a composite structure where the graphite provides a stable framework that accommodates silicon's volume changes. The silicon is contained within the graphite matrix, preventing pulverization and separation
2Quantity of substance
If silicon coating layer is added to increase charge capacity, then electrical conductivity is improved, but volume expansion still occurs
Solution Approach 1:
Different regions of the anode material have different properties: the graphite regions provide dimensional stability and structural framework, while the silicon regions provide high lithium capacity. The composite structure creates local quality variations that simultaneously achieve both stability and high capacity
Solution Approach 2:
The invention uses a composite material system combining graphite and silicon in specific ratios and configurations. This composite approach leverages the complementary properties of both materials: graphite's stability and silicon's high capacity, achieving performance that neither material could provide alone
3Reliability
If graphite is used as anode active material to ensure structural stability, then reliability is improved, but charge capacity is limited to near theoretical capacity
Solution Approach 1:
The invention merges graphite and silicon into a composite anode material that combines the structural stability of graphite with the high capacity of silicon. The two materials work synergistically to achieve both reliability and enhanced charge capacity beyond what graphite alone can provide
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 excellent charge capacity and electrical conductivity by effectively managing silicon's volume changes, improving battery performance.
Implementation Method 1
a primary coating layer filling the first space and coated on the inner surface of the second space in the particle
Implementation Method 2
silicon undergoes a volume expansion of three times or more due to changes in the crystal structure when alloyed with lithium
Implementation Method 3
capable of attaining excellent charge capacity and electrical conductivity
Data Source
AI summary
Disclosed is an anode active material for a lithium secondary battery, capable of attaining excellent charge capacity and electrical conductivity, by selectively filling a space of a porous particle with a diameter no larger than a specific size that cannot accommodate the volume change of silicon and coating a primary carbon coating layer, a silicon coating layer, and a secondary carbon coating layer in a space of the porous particle with a diameter no smaller than a specific size that can accommodate the volume change of silicon.