Carbon-Coated Spherical Graphite Anode for Low-Porosity Electrodes
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Solution Overview
Problem
Existing carbonaceous negative electrode active materials, particularly those derived from spheronized natural graphite, suffer from high internal porosity, reduced density, and poor sphericity, leading to issues such as electrode swelling, irreversible reactions, and degradation of high-temperature storage characteristics due to exposed graphite edges and large internal pores.
Innovation Solution
A method involving the spheronization of scaly graphite with a mixture of solid and liquid pitch, followed by firing, carbon coating, and heat treatment, reduces internal pores and improves sphericity, resulting in a spheronized carbonaceous negative electrode active material with controlled porosity and enhanced stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If natural graphite is spheronized to improve surface smoothness and processability, then electrode processability is improved, but internal pores increase and density decreases
Solution Approach 1:
The patent applies preliminary carbon coating to the surface of natural graphite particles before spheronization. This pre-coating creates a protective layer that fills surface defects and reduces internal pore formation during the subsequent spheronization process, thereby maintaining density while improving surface smoothness and processability
Solution Approach 2:
The patent creates a composite structure by coating natural graphite with carbon material, forming a core-shell structure where the carbon coating layer encapsulates the graphite core. This composite approach reduces internal porosity while maintaining the beneficial spherical shape and processability
2Reliability
If low-crystalline carbon coating is applied to prevent graphite edge exposure, then electrode stability is improved, but coating film breaks during densification and graphite edges become exposed
Solution Approach 1:
The patent changes the crystalline structure parameter of the carbon coating from low-crystalline to high-crystalline form. This parameter change significantly improves the mechanical strength and integrity of the coating film, preventing it from breaking during the densification process while maintaining electrode stability
Solution Approach 2:
The patent employs spheronization to create highly spherical particles with smooth surfaces. This spherical morphology distributes mechanical stresses uniformly during densification, preventing coating film rupture and maintaining edge protection throughout the electrode manufacturing process
3Shape
If spheronization is performed on scaly graphite, then sphericity is improved, but internal pores are generated and density is reduced
Solution Approach 1:
The patent applies carbon coating to the scaly graphite particles before spheronization. This preliminary coating acts as a binding agent that fills internal voids and pores during the spheronization process, enabling the formation of dense spherical particles without generating excessive internal porosity
Solution Approach 2:
The patent utilizes controlled porosity management by initially having porous scaly graphite, then through spheronization with carbon coating, transforms it into a material with optimized pore structure - reducing harmful internal pores while maintaining beneficial porosity for electrolyte penetration
4Ease of manufacture
If graphite edge surfaces are exposed due to coating film breakdown, then manufacturing simplicity is maintained, but irreversible reactions and electrolyte destruction occur
Solution Approach 1:
The patent creates a composite structure with carbon-coated spherical graphite particles where the carbon coating layer serves as a protective barrier. This composite approach prevents direct exposure of reactive graphite edges to electrolyte, eliminating irreversible reactions while maintaining manufacturing simplicity
Solution Approach 2:
The carbon coating layer acts as an intermediary between the graphite core and the electrolyte. This intermediate layer prevents direct harmful interactions between graphite edges and electrolyte, blocking irreversible reactions while allowing ionic transport, thus maintaining both manufacturing simplicity and chemical stability
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 method produces a carbonaceous negative electrode active material with reduced internal stress, improved swelling characteristics, and enhanced high-temperature storage capacity, contributing to a more stable and efficient lithium secondary battery performance.
Implementation Method 1
mixing scaly graphite, solid pitch and liquid pitch to form a mixture, and spheronizing the mixture to prepare spheronized granulated particles; firing the spheronized granulated particles
Implementation Method 2
carrying out carbon coating of the fired spheronized granulated particles to form carbon-coated spheronized granulated particles
Implementation Method 3
heat treating the carbon-coated spheronized granulated particles
Data Source
AI summary
A method for preparing a spheronized carbonaceous negative electrode active material, including the steps of: mixing scaly graphite, solid pitch and liquid pitch to form a mixture, and spheronizing the mixture to prepare spheronized granulated particles; firing the spheronized granulated particles; carrying out carbon coating of the fired spheronized granulated particles to form carbon-coated spheronized granulated particles; heat treating the carbon-coated spheronized granulated particles; and disintegrating the heat treated carbon-coated spheronized granulated particles.