Silicon-Based Alloy Negative Electrode for Lithium Battery
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium batteries using silicon-based active materials face challenges with volume change during charging and discharging, leading to reduced cycle lifespan due to the large volume expansion of active silicon particles, which damages the material and disrupts the conducting path, resulting in deteriorated battery performance.
Innovation Solution
A silicon-based alloy represented by Si-M1-M2-C—B is developed, where M1 and M2 are selected from various metals, and C and B are added to minimize volume change, with C and B being dispersed within or on the alloy to form a stable matrix that buffers the expansion, improving the alloy's electrochemical stability and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based active material is used to increase battery capacity, then battery capacity is improved, but volume change during charging and discharging increases
Solution Approach 1:
The patent embeds silicon particles within a porous carbon matrix structure, creating a nested configuration where the silicon is contained within the carbon framework. This nesting approach allows the silicon to expand and contract during lithium insertion/extraction cycles while the surrounding carbon matrix provides structural containment, thus maintaining high battery capacity from the silicon while controlling overall volume change.
Solution Approach 2:
The patent creates a composite material system combining silicon particles with carbon matrix and additional elements (M1, M2, C, B). The silicon provides high capacity while the carbon matrix and alloying elements work together to constrain volume expansion. The composite structure leverages the advantages of each component: silicon for capacity, carbon for structural stability, and alloying elements for volume control and conductivity maintenance.
2Quantity of substance
If silicon particles expand during charging, then lithium insertion capacity is improved, but conducting path is disrupted
Solution Approach 1:
The patent employs a porous carbon matrix that acts as a flexible shell surrounding the silicon particles. This carbon shell can accommodate the expansion and contraction of silicon during lithium insertion and extraction while maintaining structural integrity. The flexible nature of the carbon matrix allows it to deform with the silicon volume changes without breaking the conducting paths, thus preserving both lithium insertion capacity and electrical conductivity.
Solution Approach 2:
The carbon matrix serves as an intermediary between the silicon particles and the external circuit. It provides continuous electrical conductivity pathways that are not directly affected by silicon volume changes. The carbon matrix mediates the mechanical stress and volume expansion, preventing direct disruption of conducting paths while still allowing efficient electron transport to and from the silicon particles during lithium insertion/extraction.
3Quantity of substance
If silicon-based material is used to enhance capacity, then battery capacity is improved, but cycle lifespan is reduced
Solution Approach 1:
The patent incorporates a porous carbon matrix structure before the silicon particles undergo repeated expansion and contraction cycles. This pre-formed carbon cushioning structure provides mechanical support and stress distribution from the beginning, preventing the silicon particles from experiencing uncontrolled volume changes that would lead to fragmentation and conductivity loss. The carbon matrix absorbs and distributes mechanical stress, thereby extending the cycle lifespan while maintaining high capacity.
Solution Approach 2:
The composite material system combines silicon with carbon matrix and alloying elements (M1, M2, C, B) to create a synergistic structure. The silicon provides high lithium insertion capacity while the carbon matrix and alloying elements work together to maintain structural stability over repeated cycles. The composite structure prevents silicon particle degradation and maintains conducting paths, thereby achieving both high capacity and extended cycle lifespan.
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 silicon-based alloy with controlled composition and structure enhances the lithium battery's lifespan characteristics by maintaining stability and conductivity, even after repeated charging and discharging cycles, while maintaining a high battery capacity.
Implementation Method 1
A lithium secondary battery provides electrical energy by oxidation and reduction reactions when lithium ions are intercalated/deintercalated at a positive electrode and a negative electrode
Implementation Method 2
C and B may each be independently disposed on a surface of or inside the silicon-based alloy
Data Source
AI summary
A negative electrode active material includes a silicon-based alloy represented by Si-M1-M2-C—B, wherein M1 and M2 are different from each other and are each independently selected from magnesium, aluminum, titanium, vanadium, chromium, iron, cobalt, nickel, copper, zinc, gallium, germanium, manganese, yttrium, zirconium, niobium, molybdenum, silver, tin, tantalum, and tungsten. In the silicon-based alloy, Si is in a range of about 50 at % to about 90 at %, M1 is in a range of about 10 at % to about 50 atom %, and M2 is in a range of 0 at % to about 10 at %, based on a total number of Si, M1, and M2 atoms. C is in a range of about 0.01 to about 30 parts by weight, and B is in a range of 0 to about 5 parts by weight, based on a total of 100 parts by weight of Si, M1, and M2.