Silicon Anode Conductive Coating for Expansion and Conductivity
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Solution Overview
Problem
Silicon-based materials for negative electrodes in secondary batteries face challenges with high volume expansion and poor electronic conductivity, limiting their commercial application due to issues like pulverization and side reactions with electrolytes.
Innovation Solution
A silicon-containing negative electrode active material is developed, comprising a silicon-based material coated with a conductive layer containing a polymer with polar functional groups and one-dimensional conductive materials, where the mass ratio of silicon to polymer is controlled between 0.2 and 8, ensuring hydrogen bonding and cross-linking to enhance electronic conductivity and reduce volume expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based materials are used as negative electrode active materials, then theoretical capacity per gram increases significantly (up to 4200 mAh/g), but volume expansion and poor electronic conductivity worsen
Solution Approach 1:
The patent uses composite materials by combining silicon-based materials with conductive polymers and one-dimensional conductive materials (such as carbon nanotubes or graphene). This composite structure allows the silicon to provide high capacity while the conductive materials provide electron transport pathways and the polymer matrix accommodates volume expansion, thus resolving the contradiction between high capacity and poor conductivity/stability
Solution Approach 2:
The conductive polymer forms a flexible coating layer around the silicon-based material particles. This flexible shell structure can accommodate the volume expansion of silicon during lithium insertion without causing pulverization, while simultaneously providing continuous electronic conductivity through the polymer matrix, thus resolving the contradiction between high capacity and reliability
2Reliability
If conductive layer is added to silicon-based material, then electronic conductivity improves, but manufacturing complexity increases
Solution Approach 1:
The patent merges multiple functions into a single conductive layer coating process. The conductive polymer simultaneously provides electronic conductivity, mechanical flexibility to accommodate expansion, and binding functionality. The one-dimensional conductive materials are integrated into this layer to enhance electron transport. This merging approach improves conductivity without proportionally increasing manufacturing complexity
Solution Approach 2:
The patent optimizes parameters such as the mass percentage content of polar functional groups (A1) and silicon content (A2) with their ratio A2/A1 controlled between 0.2 to 8. By adjusting these compositional parameters, the patent achieves optimal balance between conductivity, capacity, and manufacturing feasibility, resolving the contradiction between improved reliability and manufacturing complexity
3Stability of the object's composition
If polar functional groups are increased in polymer, then hydrogen bonding and cross-linking improve conductive layer stability, but electronic conductivity may decrease
Solution Approach 1:
The patent precisely controls the mass percentage content of polar functional groups (A1) and its ratio to silicon content (A2/A1 between 0.2 to 8). This parameter optimization ensures sufficient hydrogen bonding for stability while maintaining adequate electronic conductivity by preventing excessive cross-linking that would insulate the conductive pathways
Solution Approach 2:
The patent combines conductive polymers with one-dimensional conductive materials (carbon nanotubes, graphene) to create a composite conductive layer. The polymer provides stability through hydrogen bonding, while the one-dimensional conductive materials provide electron transport pathways that are less sensitive to the polymer's cross-linking density, thus resolving the contradiction between stability and conductivity
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 good electronic conductivity, high reversible capacity, and low volume expansion, improving the energy density and cycling performance of secondary batteries.
Implementation Method 1
the polar functional group(s) in the polymer have a mass percentage content as A1, and silicon in the silicon-based material has a mass percentage content as A2, the silicon-containing negative electrode active material satisfies: A2 is from 5% to 100% and A2/A1 is from 0.2 to 8... an appropriate amount of hydrogen bondings are formed between the polar functional group(s) in the polymer and the functional groups on the surface of one-dimension conductive materials and between the polar functional group(s) in the polymer and the functional groups on the surface of the silicon-based material
Implementation Method 2
the polymer and one-dimension conductive material can crosslink and entangle with each other, making the conductive layer have flexibility and firmly cover the surface of the silicon-based material like a fishing net
Data Source
AI summary
A silicon-containing negative electrode active material may include a silicon-based material and a conductive layer, located on the surface of the silicon-based material, including a polymer and a one-dimension conductive material, wherein, the polymer may include polar functional group(s) including one or more selected form carboxylic acid group, hydroxyl group, amide groups, amino group, carbonyl group, and nitro group; and the polar functional group(s) in the polymer may have a mass percentage content as A1, and silicon in the silicon-based material may have a mass percentage content as A2, the silicon-containing negative electrode active material may satisfy: A2 is from 5% to 100% and A2/A1 is from 0.2 to 8.