Metal Phosphide-Coated Carbon Anodes for Fast-Charging Li-Ion Batteries
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Solution Overview
Problem
Lithium secondary batteries with carbon-based anode active materials face high resistance and lithium metal precipitation during high-rate charging, leading to inefficient charging and discharging and reduced lifespan.
Innovation Solution
A phosphide coating layer is formed on the surface of carbon-based materials using metal elements like Mo, Ni, Fe, Co, Ti, V, Cr, and Mn, reducing surface resistance and suppressing lithium metal precipitation through a method involving precursor layers and heat treatment in an inert gas atmosphere.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a carbon-based material is applied as an anode active material, then high energy density is achieved, but high resistance is generated during lithium ion intercalation leading to poor high-rate charging characteristics
Solution Approach 1:
A coating layer comprising a metal phosphide compound is formed on the surface of the carbon-based anode active material. This creates a localized functional layer with different properties than the bulk carbon material, specifically providing lower resistance pathways for lithium ion intercalation while maintaining the high energy density of the carbon core.
Solution Approach 2:
The invention creates a composite structure combining carbon-based material with metal phosphide compound. The composite anode active material integrates the high energy density advantage of carbon materials with the superior lithium ion conductivity of metal phosphides, resolving the contradiction between energy density and high-rate charging performance.
2Duration of action of stationary object
If surface modification is conducted to improve lithium ion mobility, then lifespan characteristics are improved, but lithium metal precipitation and capacity reduction occur during high-rate charging
Solution Approach 1:
The invention changes the chemical composition and structure of the surface coating layer by using metal phosphide compounds with specific properties. The coating layer comprises a metal phosphide compound formed by reacting a metal compound with a phosphorus compound, creating a surface layer with optimized lithium ion conductivity that prevents both lifespan deterioration and lithium metal precipitation during high-rate charging.
3Reliability
If a functional coating layer is formed to reduce resistance, then high-rate charging characteristics are improved, but charging and discharging efficiency and lifespan characteristics deteriorate
Solution Approach 1:
The coating layer is designed to provide localized functionality only where needed - on the surface of the carbon-based material where lithium ion intercalation occurs. The metal phosphide compound in the coating layer provides low-resistance pathways for lithium ion transport, improving high-rate charging characteristics without interfering with the bulk electrochemical reactions that determine charging and discharging efficiency.
Solution Approach 2:
The composite structure of carbon-based material coated with metal phosphide compound creates synergistic effects. The carbon core maintains high energy density and electrochemical stability for efficient charging and discharging, while the metal phosphide surface layer provides enhanced lithium ion conductivity for improved high-rate charging characteristics, without compromising overall efficiency or lifespan.
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 phosphide coating layer enhances high-rate charging characteristics and maintains efficient charging and discharging performance without deteriorating the battery's lifespan.
Implementation Method 1
during the intercalation of lithium ions into the carbon-based material
Implementation Method 2
suppressing the precipitation of lithium metal during high-rate charging
Implementation Method 3
reacting the precursor coating layer and the P precursor to convert at least a portion of the precursor coating layer into a compound represented by chemical formula Mex1Py1
Implementation Method 4
reacting the precursor coating layer and the P precursor to convert at least a portion of the precursor coating layer into a compound
Data Source
AI summary
The present invention provides a method for preparing an anode active material for a nonaqueous lithium secondary battery, comprising the steps of: preparing a carbon-based material; forming a precursor coating layer comprising Me and A (wherein A is O or S) on the surface of the carbon-based material; supplying a P precursor to the precursor coating layer of the carbon-based material; and converting at least a part of the precursor coating layer into a compound represented by Mex1Py1 (wherein x1>0 and y1>0) by the reaction of the precursor coating layer and the P precursor, thereby forming a phosphide coating layer, wherein Me is at least one type of the same metal element selected from among Mo, Ni, Fe, Co, Ti, V, Cr, Nb and Mn.