Si Composite Electrode with Li Metal Doping for Lithium-Ion Batteries
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Solution Overview
Problem
Lithium-ion batteries face challenges in achieving high energy density for electric vehicle applications due to low first cycle coulombic efficiency and lithium shortage in silicon anode materials, leading to electrode potential shifts and rapid cell fading.
Innovation Solution
A silicon anode electrode is developed using a combination of silicon powder, stabilized lithium metal powder (SLMP), and a conductive polymer binder, where SLMP is added in varying ratios to compensate for first cycle lithium loss and enhance electronic connectivity, and the electrode is formed with a slurry process onto a copper current collector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon anode materials are used to achieve high energy density, then gravimetric capacity is improved, but first cycle coulombic efficiency deteriorates
Solution Approach 1:
Stabilized lithium metal powder is added to the silicon anode electrode before battery assembly to pre-compensate for the lithium that will be consumed during first cycle lithiation. This preliminary addition of lithium ensures that sufficient cycleable lithium remains after the initial coating formation, preventing potential shifts and capacity fading in subsequent cycles.
Solution Approach 2:
The invention creates a composite anode material combining silicon particles with stabilized lithium metal powder and conductive binder. This composite structure leverages the high capacity of silicon while using the lithium metal powder to offset lithium loss, achieving both high energy density and improved coulombic efficiency.
2Speed
If smaller Si particle size is used to improve electrochemical performance, then reaction kinetics are improved, but first cycle irreversible capacity increases
Solution Approach 1:
The stabilized lithium metal powder is incorporated into the electrode structure before battery assembly, pre-compensating for the increased lithium consumption that occurs with smaller Si particles. This allows the use of fine particle sizes for improved kinetics without sacrificing too much capacity in the first cycle.
Solution Approach 2:
The invention changes the compositional parameters of the anode by adding lithium metal powder at specific weight ratios (0.1-5.0 wt% relative to silicon). This parameter adjustment compensates for the increased irreversible capacity loss associated with reduced particle size, maintaining overall electrode performance.
3Duration of action of stationary object
If SLMP is added to compensate for lithium loss, then cycling capability is improved, but electrode complexity increases
Solution Approach 1:
The electrode is formulated as a composite mixture of three components: silicon powder, stabilized lithium metal powder, and conductive polymer binder. This composite approach improves cycling capability by ensuring sufficient lithium content while maintaining a relatively simple mixing and coating process.
Solution Approach 2:
The conductive polymer binder serves as an intermediary that holds the silicon and lithium metal powder together, providing both mechanical integrity and electrical conductivity. This mediator enables the use of multiple active materials without significantly complicating the electrode fabrication process.
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 improves the cycling capability and energy density of lithium-ion batteries by maintaining electronic connectivity and mitigating stress from silicon volume changes, allowing for the use of high energy cathode materials and reducing lithium migration, thereby extending cell life and performance.
Implementation Method 1
Lithium ions are consumed during first lithiation to form surface coatings on Si, leading to a shortage of cycleable lithium in the cell
Implementation Method 2
provides improved binding force to the Si surface to help maintain good electronic connectivity throughout the electrode, and thus promote the flow of current through the electrode
Implementation Method 3
Silicon has demonstrated high gravimetric density (3579 mAh/g at Li15Si4), almost 10 times higher than graphite anode materials (372 mAh/g)
Data Source
AI summary
A silicon electrode is described, formed by combining silicon powder, a conductive binder, and SLMP™ powder from FMC Corporation to make a hybrid electrode system, useful in lithium-ion batteries. In one embodiment the binder is a conductive polymer such as described in PCT Published Application WO 2010/135248 A1.