Prelithiated Anode with Protective Polymer for Cycle Life
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Solution Overview
Problem
Lithium-ion batteries with high-capacity anode active materials face issues such as severe pulverization, reduced cycle life, and rapid capacity decay due to mechanical degradation and inadequate protective coatings, leading to low reversible capacity and poor cycling stability.
Innovation Solution
A method of prelithiating an anode by exposing it to a lithium source and an electrolyte solution to achieve a degree of lithium interaction from 5% to 100% of its maximum capacity, followed by applying a protective polymer with lithium-ion conductivity to enhance structural integrity and prevent exposure to air.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-capacity anode active materials (such as silicon, germanium, tin) are used to increase lithium storage capacity, then the reversible capacity is improved, but severe pulverization and mechanical degradation occur during charge-discharge cycles
Solution Approach 1:
The anode active material is prelithiated before being incorporated into the battery cell. This preliminary lithium insertion stabilizes the material structure and prevents severe pulverization during subsequent charge-discharge cycles, thereby maintaining high cycle life while preserving the high lithium storage capacity
Solution Approach 2:
The oxidation state of the anode active material is changed through prelithiation (e.g., converting Si to Li4.4Si). This parameter change stabilizes the material structure and prevents mechanical degradation during cycling, allowing the material to maintain both high capacity and reliability
2Strength
If protective coatings are applied to prevent pulverization, then the mechanical degradation is reduced, but the reversible capacity and cycling stability remain poor
Solution Approach 1:
Instead of applying external protective coatings that hinder lithium ion transport, the invention extracts the protection function from the coating and integrates it into the anode active material itself through prelithiation. The prelithiated material inherently resists pulverization without requiring additional coating layers
Solution Approach 2:
The invention creates a composite structure where lithium is integrated within the anode active material matrix (e.g., Li4.4Si). This composite approach provides both mechanical stability and maintains lithium ion conductivity, avoiding the capacity loss associated with traditional protective coatings
3Reliability
If conventional anode materials (graphite) are used to ensure long cycle life, then the cycling stability is improved, but the lithium storage capacity is limited
Solution Approach 1:
The anode active material is prelithiated before battery assembly, which stabilizes the structure in advance. This preliminary stabilization enables high-capacity materials to achieve long cycle life without the capacity limitations of conventional graphite
Solution Approach 2:
The invention changes the oxidation state of the anode material through prelithiation (e.g., Si to Li4.4Si), transforming it from a high-capacity but unstable material into a stable, long-cycling material that maintains its high lithium storage capacity
4Reliability
If lithium is used for SEI formation during initial cycles, then the protective layer is formed, but irreversible capacity loss occurs
Solution Approach 1:
The anode is prelithiated before battery assembly, so the material is already in its stable, lithium-rich state. This preliminary action ensures that minimal additional lithium is consumed during initial SEI formation, preserving most of the capacity for reversible cycling
Solution Approach 2:
The invention creates a copy of the final stable state (lithiated anode material) before battery assembly. By preparing the anode in its final stable configuration beforehand, the system avoids the irreversible capacity loss that would otherwise occur during initial lithium insertion and SEI formation
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 prelithiated anode with a protective polymer achieves high cycle life, reversible capacity, and compatibility with common electrolytes, effectively addressing the challenges of mechanical degradation and capacity decay.
Implementation Method 1
enabling lithium ions to intercalate into the anode active material until a level of lithium interaction, herein also referred to as a degree of prelithiation, from 5% to 100% of the maximum lithium storage capacity is achieved
Implementation Method 2
introducing a protective polymer onto the prelithiated anode to prevent exposure of the prelithiated anode active material to the open air or into the anode to bond the prelithiated anode active material
Data Source
AI summary
The disclosure provides a method of prelithiating an anode for a lithium-ion cell, the method comprising: (a) providing a pre-fabricated anode comprising an anode active material; (b) prelithiating the pre-fabricated anode by exposing the anode to a lithium source and an electrolyte solution, comprising a lithium salt dissolved in a liquid solvent, to enable lithium ions to intercalate into the anode active material until a level of lithium interaction from 5% to 100% of the maximum lithium storage capacity is achieved to form a prelithiated anode; and (c) introducing a protective polymer onto the prelithiated anode to prevent exposure of the prelithiated anode active material to the open air or into the anode to bond the prelithiated anode active material or to improve a structural integrity of the prelithiated anode, wherein the protective polymer has a lithium-ion conductivity from 10−8 S/cm to 5×10−2 S/cm at room temperature.