Silicide Nanowire Electrode with Intermediate Layer for Stress Relaxation
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Solution Overview
Problem
Lithium ion cell electrodes face challenges due to the swelling of electrochemically active materials like silicon during lithiation, which leads to stress concentration at the interface with conductive substrates, causing delamination and capacity losses, and potential safety issues like internal electrical shorts.
Innovation Solution
A nanostructured template with an electrochemically active material layer and intermediate layers to enhance adhesion, conductivity, and stress relaxation, using materials like silicide nanowires and moderating additives to reduce swelling and improve mechanical and electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If electrochemically active materials like silicon are used to increase capacity, then energy density is improved, but swelling during lithiation causes stress concentration and delamination
Solution Approach 1:
The patent implements a nested multi-layer structure where the electrochemically active material layer is sandwiched between a conductive substrate and an intermediate layer. This nested arrangement allows the intermediate layer to absorb expansion stress from the active material during lithiation, preventing stress concentration at the substrate interface and eliminating delamination while preserving high lithium capacity
Solution Approach 2:
The intermediate layer serves as a mediator between the conductive substrate and the electrochemically active material layer. It provides mechanical compliance to accommodate volume changes of the active material during cycling, maintains intimate electrical contact, and prevents direct stress transmission to the substrate, thereby resolving the contradiction between high capacity and interface stability
2Ease of manufacture
If the electrode structure is simplified to reduce manufacturing complexity, then ease of manufacture is improved, but adhesion and stress management deteriorate
Solution Approach 1:
The patent applies local quality by introducing an intermediate layer specifically at the critical substrate-active material interface where adhesion and stress management are needed. This targeted approach enhances interface stability only where required, without complicating the overall electrode structure or manufacturing process. The intermediate layer can be deposited using standard techniques, maintaining ease of manufacture while solving the adhesion problem
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 effectively mitigates interface delamination, maintains battery performance by preventing material islanding and detachment, and enhances the stability and energy density of lithium ion cells.
Implementation Method 1
The first intermediate layer may facilitate adhesion between the nanostructured template and the electrochemically active material layer
Implementation Method 2
The first intermediate layer may facilitate electronic conductivity by reducing electronic resistance between the nanostructured template and the electrochemically active material layer
Implementation Method 3
The first intermediate layer may facilitate stress relaxation between the nanostructured template and the electrochemically active material layer because the first intermediate layer has elastic properties that allow it to absorb at least some of the stress from expansion and contraction of the electrochemically active material layer
Implementation Method 4
at least a portion of the electrochemically active material layer further includes a moderating additive that reduces swelling of the electrochemically active material layer upon lithiation
Data Source
AI summary
Provided herein are novel template electrode materials and structures for lithium ion cells. Related methods are also provided. According to various embodiments, an electrode can include a nanostructured template, an electrochemically active material layer coating the template, and a first intermediate layer between the nanostructured template and the electrochemically active material layer. In one arrangement, the nanostructured template includes silicide nanowires. The electrochemically active material may be any of silicon, tin, germanium, carbon, metal hydrides, silicides, phosphides, and nitrides. The first intermediate layer may facilitate adhesion between the nanostructured template and the electrochemically active material layer, electronic conductivity within the electrode, and/or stress relaxation between the nanostructured template and the electrochemically active material layer.