Graphite Anode Material With Pore Filling to Suppress Li Plating
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Solution Overview
Problem
The existing negative electrode active materials for lithium ion secondary batteries suffer from poor storage characteristics and metal lithium precipitation issues due to high reactivity with Li ions, particularly in the uncoated pore portions of graphite particles, leading to electrolyte decomposition and precipitation during large current pulses.
Innovation Solution
A negative electrode active material is developed, comprising graphite particles coated with amorphous carbon and insulating inorganic particles, such as boehmite or nanodiamond, where the insulating particles fill the pores of the graphite with a size of 1 μm or less, reducing reactivity and enhancing storage characteristics and metal lithium precipitation resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If graphite particles are coated with amorphous carbon on the surface, then the surface reactivity with Li ions is reduced, but the pore portions remain uncoated and highly reactive causing electrolyte decomposition
Solution Approach 1:
The patent utilizes the porous structure of graphite particles and intentionally fills the pores with insulating inorganic particles. The pore portions of the graphite particles serve as receptacles for the insulating inorganic particles, ensuring that even the previously uncoated high-reactivity pore surfaces are now occupied by inert material, thereby eliminating electrolyte decomposition at these sites
Solution Approach 2:
The patent creates a composite structure combining graphite particles (conductive, active material) with insulating inorganic particles (non-conductive, pore-filling). This composite approach allows the conductive graphite to maintain its electrochemical function while the insulating particles occupy and neutralize the harmful pore surfaces, resolving the contradiction between surface coating and pore reactivity
2Reliability
If graphite particles are coated with amorphous carbon on the surface, then surface protection is improved, but pore portions become starting points for Li precipitation during large current pulses
Solution Approach 1:
The patent exploits the pore structure of graphite particles as the primary mechanism to prevent Li precipitation. By filling these pores with insulating inorganic particles, the patent eliminates the high-reactivity sites that would otherwise serve as nucleation points for metal lithium deposition during high-current charging operations
Solution Approach 2:
The insulating inorganic particles act as intermediary elements between the graphite pore surfaces and the electrolyte/Li ions. These particles physically occupy the pore spaces and prevent direct contact between Li ions and the graphite pore surfaces, thereby eliminating the starting points for Li precipitation while maintaining the overall structure and function of the negative electrode
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 proposed solution significantly improves the storage characteristics and metal lithium precipitation resistance of lithium ion secondary batteries by reducing excessive reactions with the electrolyte and preventing Li precipitation, as demonstrated by increased limiting current values and capacity retention rates.
Implementation Method 1
The insulating inorganic particle is present in the pore of the graphite particle
Data Source
AI summary
A negative electrode active material herein disclosed is a negative electrode active material for a lithium ion secondary battery. The negative electrode active material includes a graphite particle coated on the surface with an amorphous carbon and an insulating inorganic particle. The graphite particle has a pore of 1 μm or less. The insulating inorganic particle has an average particle diameter (D50) of 100 nm or less, and is present in the pore of the graphite particle.