Thermal Battery Lithium Anode Foam for Fast Impregnation and Stability
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Solution Overview
Problem
Existing anode materials for thermal batteries, such as Li-Si alloys and liquid lithium electrodes, face limitations in molding, self-discharging, and specific capacity, necessitating the development of alternative anode materials that can maintain stability and performance over extended periods without self-discharging.
Innovation Solution
A lithium anode is manufactured by immersing a metal alloy foam with a predetermined composition ratio of nickel, iron, chromium, and aluminum or molybdenum in molten lithium, facilitating lithium impregnation and reducing reactivity, which is then used in a thermal battery configuration without the need for additional surface treatments or structural supports.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If Li-Si alloys are used as anode materials, then the anode can be manufactured through powder molding method, but the molding is limited and open-circuit voltage is lower (1.9V compared to 2.0V)
Solution Approach 1:
The patent uses porous nickel foam as a substrate with controlled pore size and distribution. The porous structure allows molten lithium to penetrate and impregnate the foam, creating a lithium-filled anode structure that maintains structural integrity while enabling high lithium content and voltage performance.
Solution Approach 2:
The patent creates a composite structure combining nickel foam substrate with impregnated lithium and eutectic salt coating. This composite approach leverages the structural benefits of nickel foam, the electrochemical benefits of lithium, and the protective/functional benefits of eutectic salt coating to achieve both manufacturability and high performance.
2Reliability
If liquid lithium electrodes with iron powder are used, then the open-circuit voltage is high (2.0V), but specific capacity reduces due to excess iron powder needed to prevent leakage
Solution Approach 1:
The porous nickel foam provides a three-dimensional network that physically confines lithium, preventing leakage without requiring excessive iron powder. The pore structure naturally contains the lithium while maintaining electrical connectivity, thereby preserving specific capacity.
Solution Approach 2:
The patent employs eutectic salt coating as a sacrificial or consumable layer that manages lithium behavior at the surface. This coating can be optimized in thickness and composition to provide adequate protection and functionality with minimal impact on overall lithium content and capacity.
3Stability of the object's composition
If Li-Si alloys are used, then the anode structure is stable for storage, but self-discharging occurs and performance reduces over more than 10 years
Solution Approach 1:
The eutectic salt coating creates a chemically inert barrier between the lithium and the external environment, preventing unwanted chemical reactions and self-discharging during long-term storage. This protective layer maintains the lithium in a stable, non-reactive state until activation.
Solution Approach 2:
The composite structure of nickel foam + lithium + eutectic salt coating provides multiple layers of stability. The nickel foam provides structural framework, the lithium provides electrochemical activity, and the eutectic salt coating provides chemical stability and protection against self-discharging, achieving both structural integrity and long-term reliability.
4Reliability
If thermal battery is activated by melting solid electrolyte, then the battery can be stored for over 10 years without self-discharging, but the activation process takes time and requires high temperature
Solution Approach 1:
The thermal battery utilizes the phase transition of the electrolyte from solid to liquid upon heating to activate the battery. The eutectic salt coating on the anode also benefits from this thermal processing, as the controlled melting and cooling cycles enhance lithium distribution and activate the electrochemical pathways without requiring excessive time or temperature.
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
This approach significantly reduces operation time and cost, enhances specific capacity, and improves long-term storage properties by allowing lithium impregnation within minutes and preventing corrosion, thus maintaining the structural integrity and performance of the thermal battery.
Implementation Method 1
immersing a metal alloy foam with a predetermined composition ratio including nickel, iron, chromium, and aluminum or molybdenum in molten lithium, facilitating lithium impregnation
Implementation Method 2
the chromium in the composition ratio may facilitate the impregnation of the lithium into the pores and reduce the reactivity of the metal alloy foam with the lithium at an operating temperature of the thermal battery
Data Source
AI summary
A lithium anode of a thermal battery may include a metal alloy foam in which a plurality of pores is formed and including nickel (Ni), iron (Fe), chromium (Cr), and aluminum (Al) mixed in a predetermined composition ratio, and lithium impregnated into the metal alloy foam in a molten state and accommodated in the pores, wherein the chromium in the composition ratio may facilitate the impregnation of the lithium into the pores and reduce the reactivity of the metal alloy foam to the lithium at an operating temperature of the thermal battery, and the aluminum in the composition ratio may facilitate the impregnation of the lithium into the pores and prevent the lithium from penetrating into a surface of the metal alloy foam.