Graphite Anode Coating for High-Temperature Li-Ion Storage
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Solution Overview
Problem
Lithium-ion batteries using synthetic graphite as an anode active material suffer from poor storage performance at high temperatures due to surface defects and side reactions with the electrolyte, leading to irreversible capacity loss and reduced cycling performance.
Innovation Solution
A method involving the preparation of an anode active material by mixing synthetic graphite with sodium tetraborate and amorphous carbon, followed by spray-drying and high-temperature heating to form a uniform coating layer on the graphite surface, reducing surface defects and side reactions, and enhancing high-temperature stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If natural graphite is used as anode active material, then theoretical capacity and cost are improved, but volume expansion rate and surface defects increase leading to excessive SEI film formation and capacity loss
Solution Approach 1:
The patent applies local quality by creating a non-uniform coating structure where amorphous carbon selectively fills surface defects and voids of the graphite particles. The coating is not uniform throughout but specifically targets the defective surface regions, thereby locally improving the material properties where needed most to reduce SEI formation while preserving the high capacity characteristics of natural graphite.
Solution Approach 2:
The patent uses composite materials by combining natural graphite particles with amorphous carbon coating and boron-containing compounds. This composite structure leverages the high theoretical capacity of natural graphite while the amorphous carbon and boron compounds compensate for surface defects, creating a synergistic material that achieves both high capacity and improved cycling stability.
2Stability of the object's composition
If synthetic graphite is used as anode active material, then stability and surface consistency are improved, but storage performance at high temperature deteriorates
Solution Approach 1:
The patent introduces boron-containing compounds as an intermediary substance that mediates between the graphite surface and the electrolyte environment at high temperatures. The boron compounds form protective layers or modify the surface chemistry, acting as a buffer that prevents direct harmful interactions between the graphite and the high-temperature electrolyte, thereby improving storage performance while maintaining surface consistency.
3Reliability
If graphite particles are coated with amorphous carbon, then surface defects are reduced and SEI film formation is suppressed, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-coating the graphite particles with amorphous carbon and boron-containing compounds before battery assembly. This pre-treatment ensures that the surface defects are already filled and protected before the battery enters service, preventing the formation of excessive SEI film during initial cycling and eliminating the need for complex post-manufacturing treatments or conditioning procedures.
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 solution improves the conductivity, cycling performance, and storage capacity retention of the anode active material, particularly at high temperatures, by reducing surface defects and side reactions, and enhancing the material's antioxidant properties.
Implementation Method 1
in step 2, spray-drying the mixed slurry, and solid particles obtained therefrom are used as a precursor
Implementation Method 2
in step 3, heating the precursor for 18 ̃34 hours at 2000 ̃3000° C. so as to prepare and obtain the anode active material
Implementation Method 3
heating the precursor for 18 ̃34 hours at 2000 ̃3000° C. so as to prepare and obtain the anode active material
Implementation Method 4
During the subsequent heating process of the precursor, sodium tetraborate may infiltrate into the graphite material and transform into high-temperature antioxidant substance
Implementation Method 5
transform into high-temperature antioxidant substance, filling the internal gaps of the graphite material and covering the graphite surface, which may play a role in isolating oxidizing gases
Implementation Method 6
the contact interface between the electrolyte and the graphite particles may be reduced by forming a gap, thereby reducing the possibility of side reactions occurring at the interface
Data Source
AI summary
Provided in the present application is an anode active material, in which a preparation method of the anode active material includes steps as follows: in step 1, mixing graphite particles, sodium tetraborate and amorphous carbon, pulping with mixed particles prepared therefrom, thereby obtaining a mixed slurry, in which a feeding amount of materials mentioned above meets as follows: a mass of the graphite particles:a mass of the amorphous carbon=2˜4:6˜8, a mass of the sodium tetraborate:a mass of the graphite particles=0.07˜0.12:1, and the graphite particles include synthetic graphite; in step 2, spray-drying the mixed slurry, and solid particles obtained therefrom are used as a precursor; and in step 3, heating the precursor for 18˜34 hours at 2000˜3000° C. so as to prepare and obtain the anode active material.