Composite Anode Active Material for Lithium Battery Capacity Retention
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Solution Overview
Problem
Lithium batteries using carbonaceous anodes have low battery capacities due to porosity, and materials that alloy with lithium, such as Si or Sn, face issues like volumetric expansion and electrolytic decomposition, limiting their capacity retention and efficiency.
Innovation Solution
A composite anode active material comprising a crystalline transition metal, a crystalline intermetallic compound capable of alloying with lithium, and carbon, where the transition metal is structurally separated from the intermetallic compound, with a carbon content of less than 45 wt%, is mechanically milled with a transition metal and carbon in an inert atmosphere to form a sintered resultant, enhancing alloying capacity and capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbonaceous materials are used as anode materials to overcome metallic lithium problems, then safety and stability are improved, but battery capacity deteriorates due to low theoretical specific capacity
Solution Approach 1:
The patent uses a composite material system consisting of Sn-based intermetallic compound particles embedded in a porous carbon matrix. This composite structure combines the high capacity of alloying materials (Sn) with the stability and conductivity of carbon, achieving both improved capacity and maintained safety/stability.
Solution Approach 2:
The patent employs porous carbon materials with controlled pore structures to accommodate the volume expansion of Sn-based intermetallic compounds during lithiation. The porous structure provides buffer space, preventing particle aggregation and maintaining structural integrity, thus preserving both capacity and stability.
2Quantity of substance
If materials that alloy with lithium (Si, Sn) are used to improve battery capacity, then capacity is improved, but volumetric expansion and electrolytic decomposition occur leading to poor capacity retention
Solution Approach 1:
The porous carbon matrix provides accommodation space for the volumetric expansion of Sn-based intermetallic compounds during charge-discharge cycles. This prevents particle cracking and aggregation, maintaining structural stability and capacity retention over multiple cycles.
Solution Approach 2:
The composite structure of Sn-based intermetallic compounds embedded in carbon matrix combines the high capacity of alloying materials with the structural stability of carbon, preventing electrolytic decomposition and maintaining capacity retention.
3Stability of the object's composition
If Sn-based oxides are used to minimize particle size and prevent agglomeration, then capacity retention is improved, but irreversible capacity loss occurs due to reactions between lithium and oxygen atoms
Solution Approach 1:
The patent removes oxygen from the Sn-based compound, using Sn-based intermetallic compounds instead of Sn-based oxides. This eliminates the source of irreversible capacity loss from Li-O reactions while maintaining the benefits of minimized particle size and prevented agglomeration through the porous carbon matrix.
4Productivity
If intermetallic compounds are used to minimize particle size and prevent oxygen reactions, then initial efficiency is improved, but particle agglomeration occurs during cycling leading to degraded capacity retention
Solution Approach 1:
The porous carbon matrix physically separates and stabilizes the intermetallic compound particles, preventing their agglomeration during charge-discharge cycles. The porous structure provides a rigid framework that maintains particle dispersion and structural integrity over time.
Solution Approach 2:
The composite structure embeds intermetallic compound particles within a porous carbon matrix, combining the high initial efficiency of intermetallic compounds with the structural stability and anti-agglomeration properties of the porous carbon framework.
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 composite anode active material exhibits improved charge-discharge characteristics and increased capacity retention, outperforming traditional materials by maintaining higher discharge capacities over multiple cycles, thus addressing the limitations of existing lithium battery anodes.
Implementation Method 1
a crystalline intermetallic compound capable of alloying with lithium
Implementation Method 2
carbonaceous anodes aid in redox reactions such that lithium ions in an electrolytic solution intercalate/deintercalate in the crystal lattice structure of the carbonaceous material
Data Source
AI summary
A composite anode active material including a transition metal; an intermetallic compound which includes the transition metal as one component and is capable of alloy formation with lithium; and carbon, where both the transition metal and the intermetallic compound have crystallinity, and the transition metal exists in a phase structurally separated from the intermetallic compound capable of alloy formation with lithium, where a content of the transition metal elements as both a metal and a component of the intermetallic compound may be less than 45 wt % based on the total weight of the transition metal and the intermetallic compound capable of alloy formation with lithium. The composite anode active material is a composite anode active material having a new structure, and includes a crystalline intermetallic compound, a crystalline transition metal, and carbon. In addition, an anode and lithium battery prepared using the composite anode active material have excellent charge-discharge characteristics.