Negative Electrode Structure for Fast-Charging Li-Ion Batteries
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Solution Overview
Problem
Existing lithium-ion batteries face challenges in achieving fast charging capabilities while maintaining high energy density and preventing lithium precipitation, which can lead to safety hazards such as short circuits and explosions.
Innovation Solution
A secondary battery design that optimizes the structure of the negative electrode by controlling the surface density, density, and thickness increase of the negative electrode film, along with the lithium intercalation plateau voltage, to satisfy a specific relational formula, ensuring balanced fast charging and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the charging speed of batteries is increased, then the charging time is reduced, but the risk of lithium precipitation increases
Solution Approach 1:
The patent changes the electrochemical parameters of the negative electrode material by adjusting the lithium intercalation potential (raising it to be higher than graphite's 80mV) and controlling the potential difference between positive and negative electrodes (maintaining it between 2.5-3.5V). These parameter changes allow faster charging rates without causing lithium precipitation, as the optimized potential conditions prevent the thermodynamic conditions that lead to lithium metal formation.
2Productivity
If the surface density of negative electrode materials is reduced, then the fast charging capability is improved, but the energy density of batteries decreases
Solution Approach 1:
The patent changes the density parameter of the negative electrode film to a specific range (1.8-2.2 g/cm³) and optimizes the surface density distribution. This parameter optimization allows the electrode to achieve good fast charging performance while maintaining higher active material content, thus preserving energy density.
Solution Approach 2:
The patent introduces a dynamic thickness increase ratio (r) that ranges from 5%-20% depending on the specific embodiment. This dynamic parameter allows the electrode structure to adapt during charging, optimizing both fast charging capability and energy density by controlling how much the electrode expands during lithium insertion.
3Productivity
If the lithium intercalation potential is raised, then the fast charging performance is improved, but the voltage window may be reduced
Solution Approach 1:
The patent optimizes the voltage window parameter by controlling the potential difference between positive and negative electrodes to be between 2.5-3.5V. This parameter optimization ensures that while the lithium intercalation potential is raised for better fast charging, the overall voltage window remains sufficient for practical energy storage applications.
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 optimized battery design achieves both fast charging and improved energy density, reducing the risk of lithium precipitation and enhancing safety.
Implementation Method 1
lithium ions are deintercalated from a positive electrode material and intercalated into a negative electrode material via an electrolyte
Implementation Method 2
coating the slurry for the negative electrode active material layer on at least one surface of a negative electrode current collector to obtain a negative electrode plate to be calendered
Data Source
AI summary
Disclosed are a secondary battery and a preparation method thereof, including a preparation method for a negative electrode plate, the preparation method for the negative electrode plate includes: mixing a negative electrode active material, a conductive agent, and a binder uniformly in a solvent to form a slurry for a negative electrode active material layer; coating the slurry for the negative electrode active material layer on at least one surface of a negative electrode current collector to obtain a negative electrode plate to be calendered, which includes a negative electrode film formed by the slurry for the negative electrode active material layer; after calendering, forming the negative electrode plate, manufacturing a test cell using the negative electrode plate; manufacturing the secondary battery by combining the negative electrode plate, a positive electrode plate, a separator and an electrolyte solution; the secondary battery satisfies a relational formula: 0.9≤U×(1+r)/(ρ+7.4)/d/(1+5.3×ln(t))/1.335≤1.1.