Si-Enriched Ni-Ti-Sn Composite Electrode for Li-Ion Batteries
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Solution Overview
Problem
Current lithium-ion battery negative electrodes, particularly those based on tin and silicon, face significant aging issues due to mechanical and chemical degradation, including volume expansion and chemical attacks at the electrode-electrolyte interface, leading to reduced cycle and calendar lifespans.
Innovation Solution
The development of mixed Ni-Ti-Si/Sn composite materials with a high Si content, dispersed in a Ti-Ni-(Sn/Si) composite matrix, which minimizes volume expansion through predictive modeling, absorbs residual volume variations using shape memory alloys, and is protected by a flexible passivation layer to prevent chemical degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If intermetallic materials based on tin or silicon are used for negative electrodes, then high energy density is achieved, but mechanical degradation occurs due to volume variations during cycling
Solution Approach 1:
The electrode material is segmented into a composite structure consisting of tin or silicon active species dispersed in a deformable matrix. This segmentation allows the active species to maintain high energy density while the matrix provides mechanical stability and absorbs volume variations during lithium insertion/extraction cycles.
Solution Approach 2:
A composite material is formed by combining tin or silicon with a deformable matrix material. The composite structure enables the electrode to simultaneously achieve high energy density from the active species and mechanical stability from the matrix, which accommodates volume expansion and contraction during cycling.
2Use of energy by moving object
If intermetallic materials based on tin or silicon are used for negative electrodes, then high energy density is achieved, but chemical degradation occurs at the electrode-electrolyte interface
Solution Approach 1:
A passivation layer is introduced as an intermediary between the electrode material and the electrolyte. This layer protects the tin or silicon active species from direct chemical attacks by the electrolyte while still allowing lithium ion transport, thereby maintaining high energy density while reducing chemical degradation.
Solution Approach 2:
The composite electrode structure includes a passivation layer combined with the active tin or silicon species. This composite approach provides both high energy density from the active material and chemical protection from the passivation layer, reducing harmful chemical attacks at the interface.
3Reliability
If volume expansion is controlled to minimize degradation, then mechanical stability is improved, but capacity is reduced due to loss of active species
Solution Approach 1:
The deformable matrix is strategically designed to provide mechanical stability and volume accommodation in specific regions, while the tin or silicon active species are distributed throughout to maintain high overall capacity. This local differentiation allows the matrix to absorb volume variations without sacrificing active species quantity.
Solution Approach 2:
The composite structure combines the deformable matrix with dispersed active species, allowing the matrix to handle volume expansion mechanically while the active species maintain their electrochemical functionality. This preserves both mechanical stability and active species quantity, avoiding capacity loss.
4Reliability
If passivation layers are applied to protect from chemical attacks, then chemical stability is improved, but adhesion to the electrode material deteriorates
Solution Approach 1:
The passivation layer is designed with specific physical and chemical parameters that enable both chemical protection and good adhesion. By optimizing the composition, thickness, and structure of the passivation layer, the system achieves chemical stability while maintaining strong bonding to the electrode material through controlled interface properties.
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
These composite materials achieve high energy density with minimized volume expansion, improved mechanical stability, and enhanced chemical protection, leading to extended cycle life and increased capacity retention in lithium-ion batteries.
Implementation Method 1
absorption of the residual volume expansion by dispersion of active species in systems of deformable inactive species, called with 'shape memory'
Implementation Method 2
absorb this expansion, as well as to protect the electrode from chemical attacks
Implementation Method 3
protect the electrode from chemical attacks. We then observe the formation of a layer at the interface (SEI) which is interesting if it is thin and stable
Implementation Method 4
stable passivation thanks to flexible Ni2SnP type solders
Implementation Method 5
a high energy density with minimized volume expansion (Hume-Rothery intermetallics)
Implementation Method 6
absorb this expansion, as well as to protect the electrode from chemical attacks
Data Source
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AI summary
The present invention relates to novel composite materials enriched with silicon dispersed in matrices comprising Ni, Ti and Si and/or Sn, optionally passivated. The invention also relates to the method for producing said materials and to the use of same as electrodes. The invention further relates to the aforementioned matrices and the synthesis thereof.