SiOx-Graphite Anode Composition for Cycle and Rate Performance
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Solution Overview
Problem
Silicon-based negative electrode materials in lithium-ion batteries experience rapid capacity decay and poor cycle and rate performance due to volume expansion and low electron conductivity, leading to structural instability and electrolyte blockage.
Innovation Solution
A secondary battery design incorporating SiOx (0<x<2) and graphite as negative electrode active materials, with carbon nanotubes having an aspect ratio greater than 2500:1 as conductive agents, forms a stable conductive network to maintain electron transmission and buffer mechanical stress, reducing the binder content and inactive material proportion.
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 specific capacity is improved, but capacity decay accelerates and cycle performance deteriorates due to volume expansion
Solution Approach 1:
The silicon-containing negative material particles are embedded within a graphite matrix structure, where the graphite acts as a protective shell or container for the silicon core. This nested configuration allows the silicon to expand and contract during lithiation/delithiation cycles while being constrained by the graphite framework, preventing structural collapse and maintaining electrical contact, thus improving cycle performance while retaining high capacity
Solution Approach 2:
The negative electrode employs a composite structure combining silicon-containing materials (such as silicon oxide, silicon oxyfluoride, or silicon carbide) with graphite. This composite material approach leverages the high theoretical capacity of silicon while utilizing graphite's structural stability and conductivity to mitigate silicon's volume expansion issues, achieving both high energy density and good cycle life
2Quantity of substance
If silicon-based material is used as negative electrode active material, then specific capacity is improved, but electron conductivity decreases causing polarization
Solution Approach 1:
Conductive additives such as carbon black, conductive polymers, or metal nanoparticles are introduced as intermediary materials within the negative electrode composite. These conductive agents form a percolating network that facilitates electron transport throughout the electrode, bridging the conductivity gaps created by silicon particles and reducing polarization effects during high-rate charge-discharge operations
Solution Approach 2:
The negative electrode employs a composite structure combining silicon-containing materials (such as silicon oxide, silicon oxyfluoride, or silicon carbide) with graphite. This composite material approach leverages the high theoretical capacity of silicon while utilizing graphite's structural stability and conductivity to mitigate silicon's volume expansion issues, achieving both high energy density and good cycle life
3Quantity of substance
If binder content is reduced to increase energy density, then inactive material proportion decreases, but structural stability deteriorates
Solution Approach 1:
The graphite matrix and conductive agent network within the composite negative electrode structure provide inherent mechanical support and structural integrity, reducing the dependency on traditional binders. The conductive agent framework acts as a self-supporting skeleton that maintains electrode structure during cycling, allowing for reduced binder content while preserving structural stability and maximizing active material loading
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 design enhances cycle and rate performance while maintaining high energy density by stabilizing the electrode structure and preventing active material peeling and conductive path blockage, thus improving battery longevity and efficiency.
Implementation Method 1
carbon nanotubes with a specific aspect ratio as the conductive agent... forms a stable conductive network to maintain electron transmission
Implementation Method 2
carbon nanotubes with a specific aspect ratio as the conductive agent... buffer mechanical stress, reducing the binder content and inactive material proportion
Implementation Method 3
The negative electrode active material comprises SiOx (0
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.