Anode-Electrolyte Balance for Fast-Charging Lithium-Ion Cells
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Solution Overview
Problem
Lithium-ion batteries face challenges in achieving high energy density, fast charging and discharging capabilities while maintaining excellent electrochemical performance, particularly in optimizing the relationship between the anode active material and electrolyte components.
Innovation Solution
The electrochemical device incorporates an anode with a specific surface area, particle size distribution, and porosity, along with an electrolyte containing fluoroethylene carbonate (FEC) and ethyl propionate, to enhance the formation of a solid electrolyte interface (SEI) film, improve electrolyte infiltration, and reduce resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the anode active material has high specific surface area to improve lithium ion migration speed, then kinetic performance is improved, but side reaction products increase and cycle performance deteriorates
Solution Approach 1:
The patent applies local quality by creating a heterogeneous anode structure with different regions having different specific surface areas. The anode includes both fine particles (high specific surface area) for fast lithium ion migration and coarse particles (low specific surface area) for reduced side reactions. This spatial distribution of different qualities allows simultaneous optimization of kinetic performance and cycle stability.
Solution Approach 2:
The patent uses composite materials by combining anode active materials with different particle size distributions and specific surface areas in a single electrode structure. This composite approach enables the system to benefit from both high-surface-area materials (fast kinetics) and low-surface-area materials (high stability), resolving the contradiction between speed and reliability.
2Reliability
If FEC content is increased to improve SEI film formation, then capacity retention is improved, but charging resistance increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the FEC content within a specific range (0.015≤K2≤0.36 g/Ah) rather than simply increasing it. This quantitative optimization allows the system to achieve adequate SEI film formation for capacity retention while avoiding excessive FEC that would increase charging resistance. The parameter is tuned to find the optimal balance point.
Solution Approach 2:
The patent uses partial action by providing just enough FEC to form a protective SEI film without adding excessive amounts. The FEC content is controlled to be sufficient for protection but not excessive, thereby avoiding the harmful effect of increased charging resistance while still achieving the benefit of improved capacity retention.
3Speed
If anode active material particle size is reduced to improve lithium ion diffusion, then kinetic performance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the anode active material into particles with different size ranges rather than using uniformly fine particles. The patent specifies a bimodal or multimodal particle size distribution with first particles (2-10 μm) and second particles (5-20 μm). This segmentation allows the system to achieve good lithium ion diffusion through the smaller particles while maintaining manufacturability through the presence of larger particles that are easier to handle and process.
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 improves the cycle performance and kinetic performance of the lithium-ion battery by facilitating faster lithium ion migration and reducing the formation of side reaction products, leading to enhanced capacity retention and reduced charging resistance.
Implementation Method 1
The electrolyte includes fluoroethylene carbonate (FEC), and the electrochemical device meets the following relationship... improves the cycle performance and kinetic performance of the lithium-ion battery by facilitating faster lithium ion migration and reducing the formation of side reaction products
Implementation Method 2
facilitating faster lithium ion migration
Implementation Method 3
the anode includes an anode current collector and an anode active material layer disposed on the anode current collector
Data Source
AI summary
An electrochemical device, including a cathode, an anode and an electrolyte. The anode includes an anode current collector and an anode active material disposed on the anode current collector, the electrolyte includes fluoroethylene carbonate, and the electrochemical device meets the following relationship: 17.55≤K1−K2−1.63K32+11.27K3≤20.80, where K1 represents a specific surface area value of the unit mass of the anode active material (in m2/g), and 1.0≤K1≤2.0; K2 represents a content value of the fluoroethylene carbonate required by per Ah capacity (in g/Ah), and 0.05≤K2≤0.25; and K3 represents a weight value of the anode active material required by per Ah capacity (in g/Ah).