Silicon Anode Coating for Phase-Stable Lithium Secondary Batteries
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Solution Overview
Problem
Lithium secondary batteries with silicon negative electrode active materials face issues of phase separation and structural deterioration due to volume expansion during charge and discharge, leading to reduced battery lifespan and capacity.
Innovation Solution
A negative electrode active material is developed with a silicon core coated with a layer containing LiaVbO2 or MgH2, where 0.5<a<1.5 and 0.5<b<1.5, which suppresses phase separation by shifting the discharge reaction to a coating material at higher potentials, preventing electrical short circuits and allowing for wider discharge capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as negative electrode active material to increase energy density, then battery capacity is improved, but volume expansion during charge and discharge causes phase separation and structural deterioration
Solution Approach 1:
The negative electrode active material is segmented into a core-shell structure where silicon forms the core and a coating layer forms the shell. This segmentation allows the silicon core to provide high capacity while the coating shell constrains volume expansion and prevents phase separation, resolving the contradiction between capacity and structural stability.
Solution Approach 2:
A composite material structure is created by combining silicon with a coating material to form a core-shell composite. The silicon core provides high lithium insertion/extraction capacity while the coating material shell provides structural stability and prevents harmful phase separation, simultaneously achieving both high capacity and structural stability.
2Stability of the object's composition
If discharge potential is limited to below predetermined level to avoid phase separation, then structural stability is maintained, but available discharge capacity is reduced
Solution Approach 1:
The coating layer is applied in advance to the silicon core before electrochemical reactions occur. This preliminary protective action prevents phase separation from occurring during subsequent charge-discharge cycles, allowing the full discharge capacity of silicon to be utilized without structural deterioration.
Solution Approach 2:
The coating layer acts as an intermediary between the silicon core and the electrolyte environment. It mediates the electrochemical reactions by allowing lithium ion transport while preventing direct contact between silicon and conditions that would cause phase separation, thus enabling full capacity utilization without structural damage.
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 coating layer effectively suppresses silicon phase separation, improving battery lifespan and capacity by allowing the coating material to take over the discharge reaction at higher potentials, thus preventing pulverization and maintaining capacity.
Implementation Method 1
the most actively studied field is a field of electricity generation and electricity storage using an electrochemical reaction
Implementation Method 2
the structure of the silicon in the negative electrode in which lithium is intercalated is changed into a structure (phase separation)
Data Source
AI summary
A negative electrode active material including a core including silicon, and a coating layer disposed on at least a portion of a surface of the core and including a coating material, wherein the coating material includes at least one selected from the group consisting of LiaVbO2 and MgH2, wherein 0.5<a<1.5 and 0.5<b<1.5 is provided. Also, a negative electrode including the negative electrode active material and a lithium secondary battery including the negative electrode, are provided.