Porous Silicon Composite Electrode for Delamination-Resistant Anodes
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Solution Overview
Problem
Lithium-ion batteries face challenges with silicon anodes due to high volume expansion, leading to fractures and delamination, which affects the stability and performance of the battery, despite efforts to mitigate these issues through various structural and material modifications.
Innovation Solution
A composite electrode material is developed with a current collector having specific surface roughness and silicon layers of varying porosity, where the first silicon layer has low porosity for attachment and the second layer has higher porosity for volume expansion, reducing stress and enhancing lithium ion transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as anode material to achieve high theoretical capacity, then energy density is improved, but volume expansion causes fractures and delamination
Solution Approach 1:
The silicon anode is divided into multiple discrete silicon particles rather than a continuous bulk structure. This segmentation allows each particle to independently accommodate volume expansion during lithium insertion, preventing the formation of large-scale fractures and delamination that would occur in monolithic silicon structures.
Solution Approach 2:
Silicon particles are embedded within a porous carbon matrix structure, creating a nested configuration where silicon is contained within carbon. This nested structure provides mechanical support to the silicon particles during volume expansion, preventing fractures while maintaining electrical conductivity through the carbon matrix.
2Stability of the object's composition
If silicon particles are combined with carbon materials to reduce fractures, then structural stability is improved, but electrochemical performance may be compromised
Solution Approach 1:
A porous carbon matrix is used instead of dense carbon materials. The porous structure provides multiple benefits: it maintains structural stability during silicon expansion, preserves electrical conductivity through the porous network, and allows efficient lithium ion transport through the pores, thereby maintaining high electrochemical performance while ensuring structural stability.
Solution Approach 2:
A composite structure combining silicon particles with carbon materials is created, where each component contributes its advantageous properties. Silicon provides high theoretical capacity, carbon provides structural stability and conductivity, and their composite configuration enables both structural integrity and electrochemical performance to be achieved simultaneously.
3Reliability
If SEI passivation layer is formed on silicon surface, then electrolyte decomposition is reduced, but available electrolyte is depleted by SEI formation on fractured structures
Solution Approach 1:
A thin film SEI layer is formed on the silicon particle surfaces, which acts as a flexible protective shell. This thin film SEI provides passivation to prevent uncontrolled electrolyte decomposition while consuming minimal electrolyte, unlike thick SEI layers that would deplete available electrolyte. The flexibility of the thin film allows it to accommodate silicon volume expansion without cracking and exposing fresh surfaces that would form additional SEI.
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 electrode material improves the stability and performance of silicon anodes by preventing pulverization and delamination, maintaining electrolyte availability, and maintaining capacity retention over multiple charge-discharge cycles.
Implementation Method 1
a current collector material layer having or exhibiting a surface roughness value selected from at least one of the following: an Sdr value of more than 40%; and an Sdq value of more than 1.0
Implementation Method 2
an optional first silicon layer positioned on the current collector material layer, wherein the first silicon layer has a porosity of less than 30%
Implementation Method 3
Silicon is an attractive active anode material as it possesses a very high theoretical capacity (4200 mAh/g) and can intercalate 4.4 Li into Si. A disadvantage of silicon anodes is the very high volume expansion (>300%) that occurs during battery cycling
Implementation Method 4
at least a second silicon layer positioned on either the optional first silicon layer or the current collector material layer, wherein the second silicon layer has a porosity ranging from a porosity higher than the porosity of the optional first layer, to a porosity of less than 80%
Implementation Method 5
a solid electrolyte interface (SEI) passivation layer is formed on the surface of the battery anode via electrolyte decomposition
Data Source
AI summary
A composite electrode material, method for its production and use of the material are provided. The composite electrode material comprises: i) a current collector material layer exhibiting a surface roughness value selected from at least one of the following: —an Sdr value of more than 40%; and —an Sdq value of more than 1.0; each value being determined by white light interferometry according to standard method ISO 25178; ii) optionally, a first silicon layer positioned on the current collector material layer, wherein the first silicon layer has a porosity of less than 30%, as determined by electron microscopy; and iii) at least a second silicon layer positioned on either the optional first silicon layer or the current collector material layer, wherein the second silicon layer has a porosity ranging from a porosity higher than the porosity of the optional first layer, to a porosity of less than 80%, as determined by electron microscopy.