Pre-lithiated Silicon Anodes for Lithium Loss Reduction
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Solution Overview
Problem
Conventional silicon-containing electrodes for lithium ion batteries suffer from significant volume changes during lithium insertion/extraction, leading to cracking, capacity fade, and limited cycle life, as well as irreversible lithium loss due to the formation and breakage of the solid electrolyte interphase (SEI) layer, which limits their performance and widespread commercial use, especially in vehicle applications.
Innovation Solution
A method of pre-lithiating electroactive materials by reacting lithiating agents such as lithium hydride (LiH) or lithium nitride (Li3N) with silicon-containing materials to form lithium-containing or lithium nitride-containing metallic compounds, which are then combined with electrically conductive materials and a polymeric binder to create high-performance electrodes that minimize capacity fade and maximize charge capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-containing materials are used as negative electrode material to achieve high specific capacity, then the theoretical capacity for lithium is increased, but volume expansion and cracking occur during lithium insertion/extraction
Solution Approach 1:
The electrode is segmented into multiple small particles rather than using large bulk silicon. This segmentation allows each particle to undergo volume expansion independently, reducing mechanical stress and preventing cracking of the overall electrode structure during lithium insertion/extraction cycles.
Solution Approach 2:
A flexible polymer binder matrix is used to encapsulate the silicon particles. This flexible shell accommodates the volume expansion and contraction of silicon during cycling, maintaining structural integrity and preventing particle detachment from the current collector.
2Stability of the object's composition
If conventional negative electrodes are used to maintain structural stability, then volume changes are minimized, but first cycle active lithium losses occur due to SEI layer formation
Solution Approach 1:
The electrode structure is pre-designed with sufficient lithium inventory and a stable polymer binder matrix before battery assembly. This preliminary preparation ensures that the SEI layer forms on a stable structure, minimizing subsequent lithium loss from continuous SEI repair during cycling.
Solution Approach 2:
The invention changes the chemical composition parameters of the binder matrix by incorporating specific polymers with stable lithium interaction properties. This parameter change reduces the reactivity between the binder and lithium ions, minimizing SEI formation and associated lithium loss.
3Use of energy by moving object
If high specific capacity materials are used to maximize charge capacity, then energy density is improved, but continuous SEI breakage and re-formation cause ongoing active lithium loss
Solution Approach 1:
The electrode is designed with excess lithium inventory and a cushioning polymer matrix before battery operation. This beforehand cushioning compensates for the anticipated SEI breakage and re-formation losses during cycling, maintaining stable performance over extended cycles.
Solution Approach 2:
The polymer binder matrix performs a dual function: it holds the electrode structure together while also serving as a protective layer that reduces SEI breakage. The binder's flexible nature allows it to self-accommodate volume changes, reducing the need for continuous SEI repair and minimizing lithium loss.
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 pre-lithiation process enhances the electrochemical performance and longevity of silicon-containing electrodes, reducing irreversible lithium loss and improving the specific energy and power of lithium ion batteries, thereby addressing the limitations of conventional silicon anode materials.
Implementation Method 1
reacting a first lithiating agent including LiH with the electroactive material to form a pre-lithiated electroactive material
Implementation Method 2
reacting a second lithiating agent including Li3N with the electroactive material to form a pre-lithiated electroactive material
Implementation Method 3
Conventional lithium ion batteries operate by reversibly passing lithium ions between the negative electrode and the positive electrode
Data Source
AI summary
Methods for pre-lithiating an electroactive material including a Group III element, Group IV element, a Group V element, or a combination thereof for an electrode for an electrochemical cell are provided as well as electrodes including the pre-lithiated electroactive material. The methods include reacting a lithiating agent including LiH or Li3N with the electroactive material to form a pre-lithiated electroactive material.