SiOx-Graphite Anode Composition for Stable High-Rate Cycling
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Solution Overview
Problem
The rapid capacity decay and poor cycle and rate performance of lithium-ion batteries due to the volume expansion of silicon-based negative electrode materials, which cause electrode plate pulverization and electrolyte reflux, are addressed.
Innovation Solution
A secondary battery design incorporating a negative electrode active material of SiOx (0<x<2) with graphite and carbon nanotubes having an aspect ratio greater than or equal to 2500:1, forming a stable conductive network to maintain structural integrity and improve adhesion, thereby enhancing cycle and rate performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based material is used as negative electrode active material to increase energy density, then the specific capacity is improved, but the electrode plate structure stability deteriorates due to volume expansion during delithiation/lithiation
Solution Approach 1:
The patent uses a composite negative electrode material consisting of silicon-based particles (providing high capacity) embedded in a graphite matrix (providing structural stability). This composite structure allows the silicon to expand and contract during lithiation/delithiation while the graphite framework maintains the overall electrode integrity, preventing pulverization and maintaining structural stability throughout cycling.
2Quantity of substance
If silicon-based material is used to increase energy density, then the specific capacity is improved, but the cycle performance deteriorates due to rapid capacity decay
Solution Approach 1:
The silicon-graphite composite structure prevents rapid capacity decay by maintaining structural integrity over multiple cycles. The graphite matrix accommodates silicon volume changes without collapsing, ensuring continuous electrical contact and stable lithium ion transport pathways, which enables the battery to maintain high capacity retention after extensive cycling.
Solution Approach 2:
The patent employs a flexible binder system that forms a resilient matrix around the silicon-graphite composite particles. This flexible binding network can accommodate the dynamic volume changes of silicon during cycling while maintaining cohesive electrode structure, preventing particle detachment and electrical disconnection that would otherwise lead to rapid capacity decay.
3Quantity of substance
If silicon-based material is used to increase energy density, then the specific capacity is improved, but the rate performance deteriorates due to low electron conductivity and polarization
Solution Approach 1:
The silicon-graphite composite leverages graphite's superior electrical conductivity to compensate for silicon's low electron conductivity. The conductive graphite matrix forms continuous electron transport pathways throughout the electrode, ensuring efficient electron flow even at high current rates. This conductive network reduces polarization effects and enables the high-capacity silicon material to deliver its full potential at elevated charge/discharge rates.
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 battery achieves high energy density with improved cycle and rate performance by stabilizing the electrode structure and reducing inactive material content, preventing active material peeling and conductive path blocking during volume expansion.
Implementation Method 1
carbon nanotubes with a specific aspect ratio as the conductive agent... forming a powerful and stable conductive network
Implementation Method 2
silicon-based material will cause rapid capacity decay during the process of delithiation/lithiation
Data Source
AI summary
The embodiments of this application provide a secondary battery, and a battery module, a battery pack and an apparatus including the same. Specifically, this application provides a secondary battery, which includes a negative electrode plate. The negative electrode plate includes a negative electrode current collector and a negative electrode film disposed on at least one surface of the negative electrode current collector. The negative electrode film includes a negative electrode active material, a conductive agent, and a binder. The negative electrode active material includes SiOx (0<x<2) and graphite. An average particle diameter Dv50 of the negative electrode active material is from 8 μm to 14 μm. The conductive agent includes carbon nanotubes whose aspect ratio is greater than or equal to 2500:1. The secondary battery can have both good rate performance and cycle performance under the premise of a relatively high energy density.