Graphite Negative Electrode for High-Density Lithium Batteries
Solution Overview
Problem
Existing lithium secondary battery negative electrodes suffer from deteriorated rapid charge and discharge characteristics and cycle life due to the high aspect ratio of scaly graphite powders, which lead to internal destruction and reduced lithium absorption and release capabilities, especially at higher densities.
Innovation Solution
A negative electrode with a diffraction intensity ratio (002)/(110) of 500 or less, a density between 1.50 to 1.95 g/cm3, and an average particle diameter of graphite powders between 1 to 100 μm, along with a crystallite size of 500 Å or more in the C-axis direction, is developed to improve the energy density and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If scaly graphite powders with high aspect ratio are used in the negative electrode, then the energy density per unit volume increases, but the rapid charge and discharge characteristics deteriorate
Solution Approach 1:
The invention changes the crystallographic parameters of graphite powder by controlling the diffraction intensity ratio (002)/(110) to be 50 or more, which fundamentally alters the crystal orientation and morphology. This parameter change transforms the graphite from scaly high-aspect-ratio particles to more equiaxed particles with improved charge-discharge characteristics while maintaining high energy density
2Quantity of substance
If scaly graphite powders with high aspect ratio are used in the negative electrode, then the energy density per unit volume increases, but the cycle characteristics deteriorate
Solution Approach 1:
By changing the crystallographic parameters of graphite powder (diffraction intensity ratio (002)/(110) ≥ 50), the invention eliminates the scaly morphology that causes internal destruction during cycling. This parameter change ensures structural stability during repeated lithium insertion/extraction, improving cycle characteristics while maintaining high energy density
3Quantity of substance
If the density of the negative electrode is increased to improve energy density, then the energy density per unit volume increases, but lithium absorption and release becomes difficult
Solution Approach 1:
The invention changes the fundamental crystallographic parameters of graphite powder by ensuring the diffraction intensity ratio (002)/(110) is 50 or more. This creates a unique crystal orientation that allows high electrode density (1.45 g/cm³ or more) while maintaining excellent lithium ion diffusion pathways, enabling both high energy density and rapid lithium absorption/release
4Ease of manufacture
If scaly graphite powders are used in the negative electrode, then the manufacturing process is simple, but internal destruction occurs due to expansion and contraction
Solution Approach 1:
By changing the crystallographic parameters of graphite powder (diffraction intensity ratio (002)/(110) ≥ 50), the invention produces particles with uniform morphology and reduced aspect ratio. This parameter change eliminates the scaly structure that is prone to internal destruction, while the particles remain easy to process and manufacture into electrodes
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 solution enhances the rapid charge and discharge characteristics and cycle life of lithium secondary batteries by optimizing the graphite powder properties, leading to improved energy density and reduced irreversible capacity, while maintaining mechanical strength and thermal stability.
Implementation Method 1
a diffraction intensity ratio (002)/(110) measured by X-ray diffractometry of the layer of a mixture is 500 or less
Data Source
AI summary
A negative electrode for a lithium secondary battery, comprising a layer of a mixture containing graphite powder and an organic binder on a current collector, wherein a diffraction intensity ratio (002)/(110) measured by X-ray diffractometry of the layer of a mixture is 500 or less,and a lithium secondary battery, comprising the negative electrode for a lithium secondary battery, and a positive electrode that includes a lithium compound. It results less deterioration in the rapid charge and discharge characteristics and the cycle characteristics when the density of the negative electrode is made higher. Thereby it provides a high capacity lithium secondary battery having the improved energy density per unit volume of the secondary battery.