SiCN/BN Composite Anode for High-Capacity Li-Ion Batteries
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Solution Overview
Problem
Current lithium-ion battery (LIB) anodes, particularly graphite, suffer from poor rate capability and low charge capacity due to significant volume changes and poor electrical conductivity, limiting their performance in electric vehicles and wearable devices.
Innovation Solution
The development of polymer-derived ceramic composites incorporating a matrix of silicon carbonitride (SiCN) and/or silicon oxycarbide (SiOC) with hexagonal boron nitride nanosheets, which eliminates the need for separate conducting materials and enhances electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If graphite anode is used, then lithium-ion battery can be manufactured with conventional processes, but the rate capability and charge capacity are limited due to poor electrical conductivity and volume changes
Solution Approach 1:
The patent employs a composite material system consisting of silicon-based polymer-derived ceramic particles (SiC, SiOC, SiCN) combined with conductive carbon matrix and bound rubber. This composite structure leverages the high capacity of silicon-based ceramics while the conductive carbon matrix addresses the electrical conductivity deficiency, thereby simultaneously improving both charge capacity and rate capability
Solution Approach 2:
The patent modifies the physical and chemical parameters of the anode material by using polymer-derived ceramics with controlled composition ratios (SiC:SiOC:SiCN), particle size distributions, and crosslinking densities. These parameter changes enable optimization of both capacity and conductivity properties without sacrificing structural stability during lithium insertion/extraction cycles
2Productivity
If silicon-based anode is used to increase capacity, then charge capacity increases by more than 30%, but volume changes during charge/discharge cycles cause poor rate capability
Solution Approach 1:
The patent uses bound rubber as a flexible matrix that can accommodate volume changes of silicon-based ceramic particles during lithium insertion and extraction. This flexible matrix maintains structural integrity while allowing the rigid ceramic particles to expand and contract, thereby preventing capacity loss from volume instability
Solution Approach 2:
The composite structure of rigid silicon-based ceramic particles embedded in a flexible bound rubber matrix creates a synergistic system where the ceramic provides high capacity and the rubber provides volume stability, resolving the contradiction between capacity enhancement and compositional stability
3Ease of manufacture
If conventional graphite anode is used, then manufacturing process is simple, but electrical conductivity is poor leading to limited rate capability
Solution Approach 1:
The patent introduces conductive carbon as an intermediary material that bridges the electrical conductivity gap. The conductive carbon matrix surrounds and connects silicon-based ceramic particles, providing continuous electron transport pathways while maintaining the simplicity of conventional battery manufacturing processes
Solution Approach 2:
The patent optimizes the conductivity parameter by controlling the amount and distribution of conductive carbon in the composite, adjusting this parameter to achieve sufficient electrical conductivity without complicating the manufacturing process or sacrificing the high capacity benefits of silicon-based ceramics
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 SiCN/BN composite anode exhibits several orders of magnitude higher electrical conductivity and maintains high charge capacity and cycling stability, even at high current densities, significantly improving the performance of lithium-ion batteries.
Implementation Method 1
polymer-derived ceramic composites comprising a matrix of a polymer-derived ceramic (e.g., SiCN and/or SiOC) and hexagonal boron nitride nanosheets embedded therein
Data Source
AI summary
Polymer-derived ceramic composites are described herein. The composites are formed using hexagonal boron nitride nanosheet-functionalized silicon-based ceramic precursor polymers. The composites a matrix of a polymer-derived ceramic and hexagonal boron nitride nanosheets embedded therein. Silicon-derived ceramic precursors such as polysilazane and/or polysiloxane are used to create improved SiCN and/or SiOC ceramic composites.