Core-Shell Anode Active Material for Lithium Battery Volume Expansion Control
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Solution Overview
Problem
Lithium secondary batteries face issues with safety due to ignition and explosion risks, complex preparation processes, and insufficient discharge capacity at low temperatures, particularly with metal or metalloid oxides used as anode active materials, which lead to rapid volume expansion and irreversible phase formation.
Innovation Solution
An anode active material with a core-shell structure comprising a metal or metalloid oxide alloy coated with a thin carbon layer, where the carbon layer suppresses lithium reactivity and removes lithium by-products through acid treatment, maintaining a pH range of 7 to 10 in a water-based system to enhance cycle characteristics and volume expansion control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If metal or metalloid oxide is used as anode active material to achieve high theoretical capacity, then battery capacity is improved, but volume expansion and irreversible phase formation occur leading to poor cycle characteristics
Solution Approach 1:
The patent employs a core-shell structure where the metal or metalloid oxide core is nested within a carbon shell. The core provides high theoretical capacity through lithium alloying reactions, while the shell contains the core during volume expansion and prevents irreversible phase formation, thus maintaining cycle characteristics.
Solution Approach 2:
The patent creates a composite material system combining metal/metalloid oxide with carbon. The composite structure allows the oxide core to provide high capacity while the carbon matrix accommodates volume changes and prevents degradation, resolving the contradiction between capacity and cycle life.
2Productivity
If metal or metalloid oxide is alloyed with lithium in advance to increase initial efficiency, then irreversible phase formation is reduced, but lithium by-products remain on the surface increasing pH and weakening electrode adhesion
Solution Approach 1:
The patent extracts or removes lithium by-products from the composite surface through acid treatment. This extraction process eliminates the harmful by-products that cause high pH and weak adhesion, while preserving the beneficial lithium-alloyed core structure that provides high initial efficiency.
Solution Approach 2:
The carbon shell acts as an intermediary barrier that prevents direct contact between lithium by-products and the binder system. This intermediary layer isolates the harmful effects of by-products while allowing the underlying lithium-alloyed core to maintain high initial efficiency.
3Reliability
If carbon coating is applied to suppress lithium reactivity and remove by-products, then cycle characteristics and adhesion are improved, but manufacturing complexity increases
Solution Approach 1:
The patent optimizes the carbon coating parameters including thickness (1-10 nm), composition, and deposition conditions to achieve the desired protective function with minimal process complexity. By carefully controlling these parameters, the coating provides effective protection while maintaining a relatively simple manufacturing process.
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 core-shell structure anode active material achieves high capacity, superior cycle characteristics, and controlled volume expansion, suppressing side reactions and improving initial efficiency while maintaining electrode adhesion and stability.
Implementation Method 1
a shell part containing a carbon material coated on a surface of the core part, in which the shell part contains lithium in an amount less than 5 at % in the surface and the inner portion thereof
Implementation Method 2
the carbon layer suppresses lithium reactivity
Implementation Method 3
such anode active materials provide negative influence on performance and safety of the battery due to deteriorating cycle characteristic and excessive volume expansion with repeated charging and discharging
Data Source
AI summary
An anode active material and a method for preparing the same, wherein the anode active material has a core-shell structure having formula (MOx-Liy)-C (here, M is a metal (or metalloid), x is greater than 0 and less than 1.5, and y is greater than 0 and less than 4) and including a core part containing an alloy of a metal (or metalloid) oxide-Li (MOx-Liy) and a shell part containing a carbon material coated on a surface of the core part, wherein the shell part contains lithium in an amount less than 5 atm % in the surface and the inner portion thereof. The anode active material can provide high capacity, excellent cycle characteristics, excellent volume expansion control capability, and high initial efficiency.