Heterogeneous Metal Hydride Anode Segmentation
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Solution Overview
Problem
Magnesium hydride (MgH2) anodes in lithium ion batteries suffer from low reversibility due to the formation of an ionic compound LiH, which limits cycle stability in rechargeable batteries.
Innovation Solution
A heterogeneous metal hydride composition with discrete separate regions, comprising a main region of a first metal hydride and a secondary region of additional components such as second metal hydrides, metals, or metal compounds, which suppresses the formation of a separate LiH phase, enhancing lithium absorption and desorption properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If MgH2 is used as an anode material, then high theoretical capacity is achieved, but reversibility deteriorates due to LiH formation
Solution Approach 1:
The anode is segmented into multiple discrete regions with different compositions and functions: MgH2 regions for lithium absorption, TiH2 regions for structural stability, and LaNi5H6 regions for catalytic activity. This segmentation allows each region to perform its specialized function, preventing complete conversion to LiH and maintaining reversibility while preserving high capacity
Solution Approach 2:
The invention uses composite metal hydride materials combining MgH2 with TiH2 and LaNi5H6 in a heterogeneous structure. The composite nature provides synergistic effects: MgH2 contributes high capacity, TiH2 provides structural framework, and LaNi5H6 enhances reaction kinetics. This composite approach resolves the contradiction by maintaining both high lithium capacity and reversibility through complementary material properties
2Quantity of substance
If pure MgH2 is used, then maximum lithium absorption is achieved, but cycle stability deteriorates
Solution Approach 1:
The anode structure divides the material into separate functional regions that undergo lithium absorption/desorption in a staged manner. The MgH2 regions absorb lithium while the TiH2 and LaNi5H6 regions remain relatively stable, preventing complete structural degradation and extending cycle life while maintaining high lithium absorption capacity
Solution Approach 2:
The invention changes the physical and chemical parameters of the anode system by creating a heterogeneous composition with varying local stoichiometries and crystal structures. This parameter diversification allows different regions to respond differently to lithium insertion/extraction, improving cycle stability while preserving overall lithium absorption capacity
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 solution extends the cycle stability of the anode in rechargeable lithium ion batteries by improving lithium absorption and desorption properties, thereby enhancing the battery's performance and longevity.
Implementation Method 1
MgH2 converts to Mg embedded in a LiH matrix upon charging and MgH2 is reformed with release of lithium ions and electrons upon discharging
Implementation Method 2
MgH2 converts to Mg embedded in a LiH matrix upon charging and MgH2 is reformed with release of lithium ions and electrons upon discharging
Data Source
AI summary
Heterogeneous metal hydride (MH) compositions comprising a main region comprising a first metal hydride and a secondary region comprising one or more additional components selected from the group consisting of second metal hydrides, metals, metal alloys and further metal compounds are suitable as anode materials for lithium ion cells. The first metal hydride is for example MgH2. Methods for preparing the composition include coating, mechanical grinding, sintering, heat treatment and quenching techniques.