Graphite Negative Electrode Structure for Fast-Charging Cycle Stability
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Solution Overview
Problem
Lithium-ion batteries face challenges in achieving excellent cycle performance and kinetic performance while maintaining a high gravimetric capacity due to the limitations of natural graphite as a negative electrode material.
Innovation Solution
The electrochemical device incorporates a negative active material layer with a specific peak area ratio (SA/S002) between 0.1 and 0.3, optimized XRD peak characteristics, and controlled thickness and mass distribution to enhance intercalation and deintercalation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the thickness of the negative active material layer is reduced to improve kinetic performance and ion intercalation, then the cycle performance and ion deintercalation improve, but the energy density decreases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thickness of the negative active material layer within the range of 5-15 μm. This specific thickness parameter optimizes the balance between kinetic performance (faster ion intercalation) and energy density (sufficient active material volume), resolving the contradiction between speed and energy storage capacity.
2Use of energy by moving object
If natural graphite with high gravimetric capacity is used to improve energy density, then the cycle performance and kinetic performance deteriorate due to large-flake porous structure
Solution Approach 1:
The patent applies local quality by using spheroidized graphite particles with controlled morphology instead of large-flake natural graphite. The spherical shape and size reduction create uniform local structures that maintain high gravimetric capacity while improving cycle performance and kinetic performance through better ion access and reduced structural stress.
Solution Approach 2:
The patent employs composite materials by combining spheroidized graphite particles with specific binders and conductive agents in optimized ratios. This composite structure maintains the high capacity of graphite while adding structural integrity and conductivity that improve cycle performance and kinetic response.
3Speed
If the peak area ratio SA/S002 is increased to reduce active material layer thickness, then ion intercalation improves, but the amount of intercalatable ions decreases
Solution Approach 1:
The patent resolves this contradiction by optimizing the SA/S002 ratio within the specific range of 0.1-0.3. This parameter control ensures the active material layer thickness is optimized to allow sufficient ion intercalation rate while maintaining adequate volume for high ion capacity, balancing speed and quantity of stored ions.
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 ensures a high energy density, normal deintercalation of active metal ions, excellent cycle and kinetic performance, and a high gravimetric capacity for the electrochemical device.
Implementation Method 1
The peak area value SA of the A peak of the negative active material layer is negatively correlated with the thickness of the active material layer. The greater SA, the smaller the thickness of the negative active material layer, and the easier it is for active metal ions such as lithium ions to be intercalated in and deintercalated from the negative active material layer
Data Source
AI summary
An electrochemical device includes a negative electrode. The negative electrode includes a negative current collector and a negative active material layer. The negative active material layer includes a negative active material. The negative active material layer satisfies 0.1≤SA/S002≤0.3, where SA is a peak area value of an A peak corresponding to a diffraction angle 2θ of 42.4° to 43.6° in an XRD pattern of the negative active material layer, and S002 is a peak area value of a 002 peak in the XRD pattern of the negative active material layer. The electrochemical device has excellent cycle performance and kinetic performance in addition to a high gravimetric capacity.