Carbon-Coated Active Material Composite for High-Speed Lithium-Ion Batteries
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Solution Overview
Problem
Lithium ion batteries with carbon-coated electrode active materials face challenges in achieving high-speed charge and discharge characteristics due to insufficient electron and lithium ion conductivity, leading to increased internal resistance and voltage drops, especially when the carbonaceous film thickness and coverage are not optimally balanced.
Innovation Solution
A carbon-coated active material composite is developed with a specific activation energy range of 45 kJ/mol to 85 kJ/mol and a carbon supported amount to specific surface area ratio of 0.01 to 0.5, ensuring both electron and lithium ion conductivity, achieved by forming a carbonaceous film with a net-shaped structure and optimal thickness on the electrode active material particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the area of the surface of the lithium phosphate compound covered with the carbonaceous film is increased to improve electron conductivity, then the electron conductivity is improved, but the insertion and removal speed of lithium ions becomes slow
Solution Approach 1:
The patent applies local quality by creating a net-shaped carbonaceous film structure where carbon is distributed in a three-dimensional network rather than uniformly coating the surface. This allows different regions of the film to serve different functions: carbon-rich areas provide electron conductivity while open network regions facilitate lithium ion transport, thus resolving the contradiction between improving electron conductivity and maintaining fast lithium ion insertion/removal speed.
Solution Approach 2:
The net-shaped structure of the carbonaceous film inherently creates a porous morphology that allows electrolyte penetration and lithium ion diffusion pathways throughout the film. This porous structure enables simultaneous electron conduction through the carbon network and ion transport through the voids, resolving the trade-off between conductivity enhancement and ion transport speed.
2Reliability
If the film thickness of the carbonaceous film is increased to improve electron conductivity, then the electron conductivity is improved, but the migration speed of lithium ions in the carbonaceous film becomes slow
Solution Approach 1:
The net-shaped structure creates local variations in carbon density and film thickness, with thinner regions providing fast ion transport pathways and thicker regions providing electron conductivity, allowing the film to simultaneously achieve both functions without requiring uniform thick coverage that would slow ion migration.
Solution Approach 2:
The patent transitions from a traditional two-dimensional planar carbon coating to a three-dimensional net-shaped structure. This dimensional change creates spatial pathways that allow lithium ions to migrate through the film volume rather than being constrained to surface-level diffusion, maintaining fast ion transport even as the film provides sufficient thickness for electron conductivity.
3Reliability
If a carbonaceous film is formed on the surface of the electrode active material to increase electron conductivity, then the electron conductivity is improved, but the sum of the battery internal resistance increases
Solution Approach 1:
The net-shaped porous structure of the carbonaceous film reduces the overall resistance by providing multiple parallel pathways for both electron and ion transport. The three-dimensional network architecture decreases the tortuosity and length of transport paths compared to dense thick coatings, thereby reducing internal resistance while maintaining conductivity enhancement.
Solution Approach 2:
The carbonaceous film forms a composite structure with the lithium phosphate compound, where the net-shaped carbon network provides electron conductivity while the underlying active material provides ion storage and transport. This composite architecture optimizes the synergistic effects of both materials, achieving improved electron conductivity without proportionally increasing internal resistance.
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 solution enables lithium ion batteries to maintain low internal resistance and support high-speed charge and discharge without significant voltage drops, making them suitable for high-output power applications.
Implementation Method 1
the organic compound is carbonized, whereby a carbonaceous film is formed on the surface of the electrode active material
Implementation Method 2
a non-aqueous electrolytic solution-based secondary battery such as a lithium ion battery has been proposed and put into practical use. The lithium ion battery is constituted of a cathode and an anode which allow the reversible insertion and removal of lithium ions
Data Source
Figure 1
AI summary
A carbon-coated active material composite, an electrode and a lithium ion battery capable of improving electron conductivity and lithium ion conductivity when an electrode active material having a carbonaceous film formed on the surface is used as an electrode material are provided. In the carbon-coated active material composite, charge migration of lithium ions occurs at an interface between a carbonaceous film and an electrode active material, an activation energy of an insertion and removal reaction of lithium ions at an interface between the carbon-coated active material composite and an electrolytic solution is 45 kJ/mol to 85 kJ/mol, a value of a carbon supported amount to a specific surface area of particles of an electrode active material ([carbon supported amount]/[specific surface area of particles of electrode active material]) is 0.01 to 0.5, and the activation energy is measured using an electrolyte solution obtained by mixing ethylene carbonate and diethyl carbonate at a 1:1 ratio.