Layered Graphite Anode Structure for Fast-Charging Secondary Batteries
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Solution Overview
Problem
Existing secondary batteries suffer from slow charging times, which causes range anxiety for consumers and limits the rapid popularization of electric vehicles, despite their high energy density and long cycle life.
Innovation Solution
A secondary battery design featuring a negative-electrode plate with a multi-layer film structure, where the first negative-electrode film layer includes artificial graphite with controlled particle size distribution (Dv99 ≤ 23 μm) and specific parameters, enhancing active ion diffusion and reducing impedance for faster charging and improved energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional charging methods are used in secondary batteries, then energy density and cycle life are maintained, but charging time is excessively long
Solution Approach 1:
The patent applies local quality by creating a multi-layer negative electrode film structure where different layers have different functions: the first layer (close to current collector) uses artificial graphite with Dv99 ≤ 23 μm for fast ion diffusion and low impedance, while the second layer (outer layer) uses natural graphite for high capacity. This localized optimization of particle size and material properties in different regions of the electrode enables simultaneous achievement of fast charging capability and high energy density.
Solution Approach 2:
The patent employs composite materials by combining artificial graphite and natural graphite in a layered configuration. The artificial graphite layer provides excellent fast-charging performance with low solid-phase diffusion impedance, while the natural graphite layer contributes high theoretical capacity. This composite structure integrates the advantages of both materials to resolve the contradiction between charging speed and energy density.
2Speed
If particle size of negative electrode active material is reduced to improve fast charging, then ion diffusion speed increases, but energy density decreases
Solution Approach 1:
The patent segments the negative electrode active material into two distinct layers with different particle size characteristics. The first layer uses fine artificial graphite particles (Dv99 ≤ 23 μm) to ensure rapid ion diffusion and low impedance for fast charging. The second layer uses coarser natural graphite particles to maximize volumetric energy density. This segmentation allows each layer to optimize for its specific function without compromising the other.
Solution Approach 2:
The patent applies parameter changes by precisely controlling the particle size distribution parameter (Dv99 ≤ 23 μm) of the artificial graphite in the first layer. This specific parameter optimization creates the right balance between surface area (for fast ion diffusion) and particle density (for maintaining energy density), resolving the contradiction between ion diffusion speed and energy density.
3Device complexity
If single-layer negative electrode film is used, then structure is simple, but fast charging performance at high SOC is insufficient
Solution Approach 1:
The patent transitions from a single-layer to a multi-layer film structure, adding a dimensional aspect to the electrode design. The first layer (artificial graphite) is positioned closer to the current collector to handle fast charging demands, while the second layer (natural graphite) is positioned outward for capacity storage. This layered arrangement in the thickness dimension enables differentiated functionality that single-layer structures cannot achieve.
Solution Approach 2:
The patent applies preliminary action by pre-positioning the artificial graphite layer with optimized particle size (Dv99 ≤ 23 μm) in the first layer, which is closest to the electrolyte and current collector. This layer is prepared in advance to provide low impedance pathways and rapid ion diffusion interfaces, ensuring that when fast charging is required, the electrochemical reaction can proceed immediately at high rates without being limited by structural constraints.
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 enables high-rate charging capability and maintains cycling performance by optimizing the electrochemical reaction interface and ion diffusion, thereby addressing the slow charging issue while preserving energy density.
Implementation Method 1
the negative-electrode plate can also have a good electrochemical reaction interface and a higher solid-phase diffusion speed of active ions
Implementation Method 2
the negative-electrode plate can also have a good electrochemical reaction interface
Data Source
AI summary
A secondary battery, a preparation method thereof, and a battery module, a battery pack, and an apparatus containing such secondary battery are provided. In some embodiments, the secondary battery includes a negative-electrode plate, where the negative-electrode plate includes a negative-electrode current collector and a negative-electrode film layer, the negative-electrode film layer includes a first negative-electrode film layer and a second negative-electrode film layer, and the second negative-electrode film layer is located between the negative-electrode current collector and the first negative-electrode film layer; and the first negative-electrode film layer includes a first negative-electrode active material, the first negative-electrode active material includes a first graphite, the first graphite is artificial graphite, and a distribution of volume-based particle size Dv99 of the first negative-electrode active material is ≤23 μm.