Type II Clathrate Anodes for Rechargeable Battery Stability
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Solution Overview
Problem
Current rechargeable batteries, particularly lithium-ion batteries, face limitations in energy and power density due to the lack of suitable materials, with silicon anodes experiencing structural degradation from volume changes during lithiation and delithiation, leading to reduced cycle life and capacity retention.
Innovation Solution
The use of Type II clathrates with a formula MxX136, where X forms a cage structure and M represents guest ions, allowing for the insertion and removal of multiple guest ions like lithium, sodium, or magnesium without significant structural changes, thereby stabilizing the anode material during cycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silicon is used as anode material to achieve high capacity, then energy density is improved, but structural degradation occurs due to volume expansion during lithiation
Solution Approach 1:
The anode is segmented into multiple silicon nanowires with diameters of 50-200 nm, suspended in a porous oxide matrix. This segmentation allows each nanowire to independently accommodate volume expansion during lithiation without causing structural degradation, while maintaining high capacity. The nanoscale segmentation enables the silicon to undergo 300% volume change without fracturing.
Solution Approach 2:
Silicon nanowires are nested within a porous oxide matrix structure, creating a hierarchical composite. The oxide matrix provides structural support and accommodates the volume expansion of silicon during lithiation, while the nested configuration allows maximum contact between silicon and lithium ions. This nested structure enables the silicon to expand into the porous matrix space without compromising the overall anode structure.
2Duration of action of stationary object
If nanostructured silicon is used to prevent pulverization, then cycle life is improved, but capacity retention decreases due to agglomeration and degradation
Solution Approach 1:
A porous oxide material serves as an intermediary between silicon nanowires and the electrolyte, providing several functions: it prevents direct contact between silicon surfaces that would cause agglomeration, maintains structural integrity during cycling, and allows lithium ion transport. The oxide intermediary stabilizes the silicon nanowires throughout extended cycling while preserving capacity, preventing the degradation that occurs in pure nanostructured silicon.
3Stability of the object's composition
If engineered space is provided for silicon expansion, then structural integrity is maintained, but device complexity increases
Solution Approach 1:
A porous oxide matrix with controlled porosity is used to provide expansion space for silicon nanowires. The porous structure naturally accommodates volume changes during lithiation without requiring complex engineered cavities or constraints. The porosity provides the necessary space for 300% volume expansion while maintaining structural integrity through the oxide framework, achieving structural stability with relatively simple material selection rather than complex structural design.
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 enables extended cycling and improved capacity retention by minimizing structural damage and stress, offering higher energy density and potentially longer battery life compared to traditional silicon anodes.
Implementation Method 1
a guest ion Y is electrochemically inserted into a cage structure of a Type II clathrate having the formula MxX136 to yield a Type II clathrate having the formula MxYX136
Implementation Method 2
When Y is a lithium ion, electrochemically inserting and removing comprise lithiation and delithiation, respectively
Implementation Method 3
allowing for the insertion and removal of multiple guest ions like lithium, sodium, or magnesium without significant structural changes, thereby stabilizing the anode material during cycling
Data Source
AI summary
An anode for a rechargeable battery includes a Type II clathrate having the formula MxX136, where a cage structure is formed by X, M represents one or more guest ions, and 0<x<24. When x=0, no guest ion is present in the cage structure. X may be Si, Ge, Sn, or a combination thereof. M may be an ion of Na, K, Rb, Cs, Ba, Sr, Ca, Cl, Br, I, Eu, P, Te, Li, Mg, or a combination thereof. A rechargeable battery including the anode (e.g., as an anode) includes a cathode and an electrolyte in contact with the anode and the cathode. Forming the anode may include preparing a composition including the Type II clathrate contacting the composition with a current collector to form the anode. Guest ions may be electrochemically inserted and removed from the cage structure during operation of the rechargeable battery.