Silicon-Graphite Negative Electrode Composition for Fast-Charging Batteries
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Solution Overview
Problem
Lithium secondary batteries face limitations in increasing energy density and efficiency within a limited space due to the use of high-capacity positive electrode materials, which require higher content of negative electrode materials, leading to issues like increased resistance, gas generation, and irreversible capacity loss in non-carbon-based materials.
Innovation Solution
A negative electrode composition is developed with a specific combination of silicon carbon composite and graphite, where the tap density of graphite is equal to or greater than that of the silicon carbon composite, ensuring uniform dispersion and orientation, thereby improving ion transport and preventing particle cracking during rolling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If non-carbon-based negative electrode materials (silicon, tin, oxides) are used to increase capacity, then energy density is improved, but irreversible capacity loss increases due to low initial efficiency and large lithium consumption
Solution Approach 1:
The patent uses a composite negative electrode material consisting of silicon carbon composite particles and graphite particles. The silicon carbon composite provides high capacity while graphite provides structural stability and reversible lithium intercalation, together reducing irreversible capacity loss compared to using silicon or tin alone.
2Loss of energy
If graphite is used as negative electrode active material, then irreversible capacity loss is reduced, but energy density is limited due to small capacity per unit mass
Solution Approach 1:
The patent combines graphite (low irreversible loss) with silicon carbon composite (high capacity) in a composite structure. This allows the battery to achieve higher energy density than pure graphite while maintaining lower irreversible capacity loss than pure silicon or tin materials.
3Quantity of substance
If higher content of negative electrode materials is used to meet high-capacity positive electrode material requirements, then energy density is improved, but resistance increases and gas generation occurs
Solution Approach 1:
The composite structure of silicon carbon composite and graphite provides both high capacity and good electrochemical stability. The graphite component acts as a buffer that reduces side reactions and gas generation even at high negative electrode material content, while the silicon carbon composite contributes to high energy density.
4Quantity of substance
If negative electrode materials are increased within limited space to meet consumer demand for high energy density, then energy density is improved, but battery efficiency is limited
Solution Approach 1:
The silicon carbon composite and graphite composite structure achieves high energy density while maintaining good battery efficiency through synergistic effects: silicon carbon provides high capacity contribution while graphite ensures smooth lithium ion transport and electrical conductivity, preventing efficiency degradation even at high material loading.
Solution Approach 2:
The patent creates a composite structure where different materials are distributed to optimize local functions: silicon carbon composite particles provide high capacity regions while graphite particles provide conductive and stable regions, creating local quality variations that improve overall battery efficiency within limited space.
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
This configuration enhances rapid charging performance, efficiency, and energy density of lithium secondary batteries by ensuring uniform dispersion and orientation of graphite, reducing thickness, and preventing void regions, thus improving battery performance within a limited space.
Implementation Method 1
a tap density of the graphite is equal to or greater than a tap density of the silicon carbon composite
Implementation Method 2
intercalation and deintercalation of lithium ions at a positive electrode and a negative electrode
Implementation Method 3
The lithium secondary battery generates electric energy by oxidation and reduction reactions during intercalation and deintercalation of lithium ions
Implementation Method 4
The lithium secondary battery generates electric energy by oxidation and reduction reactions during intercalation and deintercalation of lithium ions
Data Source
AI summary
A negative electrode composition, a negative electrode, a lithium secondary battery, a battery module, and a battery pack are provided. The negative electrode composition includes a negative electrode active material comprising a silicon carbon composite and graphite, wherein a tap density of the graphite is equal to or greater than a tap density of the silicon carbon composite.