Graphite Anode Particle Hierarchy for High-Rate Lithium Batteries
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Solution Overview
Problem
Existing rechargeable lithium batteries face challenges in achieving high-rate charge and discharge characteristics without significant deterioration.
Innovation Solution
A rechargeable lithium battery design featuring a negative electrode with a negative active material comprising tertiary particles of aggregated and spheroidized secondary particles of natural graphite, surrounded by an amorphous carbon coating, which maintains a difference of about 10 mAh/g or less between X1 and X2 charge capacities during high-rate charging and discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional graphite particles are used in the negative electrode, then the battery capacity is maintained, but the high-rate charge and discharge characteristics deteriorate significantly
Solution Approach 1:
The graphite particles are segmented into primary particles (0.5-5 μm) that aggregate to form secondary particles (5-20 μm), which further aggregate to form tertiary particles (20-50 μm). This hierarchical segmentation structure allows lithium ions to efficiently penetrate smaller primary particles while maintaining overall particle integrity, significantly improving high-rate charge and discharge characteristics without causing particle disintegration
Solution Approach 2:
The invention uses composite structures where natural graphite primary particles are aggregated and spheroidized to form secondary particles, which are then aggregated with pitch carbon to form tertiary particles. This composite material approach combines the high capacity of natural graphite with the structural stability of aggregated spherical morphology, preventing deterioration during high-rate cycling
2Productivity
If graphite particles are spheroidized and aggregated to improve high-rate characteristics, then charge capacity is enhanced, but particle structure complexity increases
Solution Approach 1:
The particle structure is segmented into three hierarchical levels: primary particles (0.5-5 μm) as building blocks, secondary particles (5-20 μm) formed by spheroidized aggregation of primary particles, and tertiary particles (20-50 μm) formed by further aggregation with pitch carbon. This segmentation creates a complex but organized structure that maintains manufacturability while achieving superior high-rate performance
Solution Approach 2:
The primary graphite particles are spheroidized during the aggregation process to form spherical secondary particles. This spheroidal morphology reduces internal stress concentration and improves particle packing density, enhancing charge capacity while the regular spherical shape actually simplifies the overall particle morphology compared to irregular aggregated structures
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 high-rate charge and discharge capabilities while minimizing battery deterioration, ensuring excellent initial efficiency and cycle-life characteristics.
Implementation Method 1
an amorphous carbon coating layer surrounding the tertiary particles
Implementation Method 2
a positive electrode and a negative electrode including an active material capable of intercalating and deintercalating lithium ions
Implementation Method 3
electrical energy is produced by oxidation and reduction reactions if lithium ions are intercalated/deintercalated at the positive and negative electrodes
Data Source
AI summary
Disclosed is a rechargeable lithium battery and the rechargeable lithium battery including a negative active material including tertiary particles including graphite and aggregates of secondary particles, where the secondary particles include a plurality of primary particles that are aggregated and spheroidized; and an amorphous carbon coating layer surrounding the tertiary particles, the primary particles and the secondary particles being natural graphite; wherein if the rechargeable lithium battery is subjected to high-rate charge and discharge, a difference (X2−X1) between X1 and X2 is about 10 mAh/g or less, the X1 is a constant voltage charge capacity (X1) at which a peak point is appeared in a graph obtained by differentiating (dI1/dQ1) 1st charge capacity (Q1) by current (I1), and the X2 is a constant voltage charge capacity (X2) at which a peak point is appeared in a graph obtained by differentiating (dI2/dQ2) 50th charge capacity (Q2) by current (I2).