Pre-Lithiated Columnar Silicon Anodes for Longer-Cycle Li-Ion Cells
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Solution Overview
Problem
Lithium-ion cells with silicon anodes face challenges due to significant volume changes during charging and discharging, leading to fracturing, crumbling, and delamination, which reduce charge capacity and cycle life, and the formation of a solid-electrolyte interphase (SEI) layer consumes lithium, reducing overall capacity.
Innovation Solution
A pre-lithiated silicon anode with a columnar morphology is manufactured, allowing for pre-lithiation before cell assembly, eliminating the need for an in situ sacrificial lithium source and enhancing cycle life and capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used in the anode material to increase charge capacity, then the specific capacity increases from 370 mAh/g to 3600 mAh/g, but the volume changes by 300-400% causing fracturing and delamination
Solution Approach 1:
The silicon anode is divided into discrete silicon particles rather than using continuous silicon material. These particles are suspended in a conductive matrix, allowing each particle to expand and contract independently during lithium insertion/extraction, preventing stress concentration and structural failure.
Solution Approach 2:
The anode uses a composite structure combining silicon particles with a conductive matrix material. This composite design allows the silicon to provide high capacity while the matrix provides structural support, electrical conductivity, and stress distribution, preventing fracturing and delamination.
2Stability of the object's composition
If a thin film of silicon is deposited onto a metallic foil to maintain structural integrity, then the structural stability is improved, but the film depth is restricted to 2-5 micrometres limiting areal capacity
Solution Approach 1:
The conductive matrix is designed with a porous structure that allows silicon particles to be embedded throughout the volume. This porous architecture provides pathways for lithium ion transport while maintaining structural integrity, enabling thicker active material layers without compromising stability or capacity.
Solution Approach 2:
The invention transitions from a two-dimensional thin film architecture to a three-dimensional composite structure with silicon particles distributed throughout a volumetric conductive matrix. This dimensional change allows significantly increased areal capacity while maintaining structural stability through the matrix framework.
3Quantity of substance
If pre-lithiation is performed in situ within the cell, then the charge capacity is compensated for SEI formation, but additional sacrificial lithium source and cell complexity are required
Solution Approach 1:
The silicon particles are pre-lithiated during the electrode manufacturing process before cell assembly. This preliminary action incorporates lithium into the silicon structure in advance, eliminating the need for in-situ sacrificial lithium sources and simplifying the final cell design while still compensating for SEI formation losses.
Solution Approach 2:
The pre-lithiation process is merged with the electrode manufacturing process. The lithium incorporation is performed as part of the standard electrode fabrication steps, combining two processes into one and eliminating the need for separate in-situ pre-lithiation steps that would add cell complexity.
4Duration of action of stationary object
If the anode material is designed to accommodate volume expansion, then the cycle life is improved, but the charge capacity is reduced due to lower silicon content
Solution Approach 1:
The invention optimizes the parameters of the conductive matrix, including its composition, porosity, and mechanical properties, to provide adequate structural support for silicon expansion. By carefully tuning these parameters, the matrix can accommodate volume changes without requiring excessive matrix material, thus maintaining high silicon content and charge capacity while ensuring long cycle life.
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-lithiated silicon anode with a columnar structure provides exceptional cycle-life and capacity properties while avoiding the need for an in situ sacrificial lithium source, resulting in improved performance and reduced mass for the lithium-ion cell.
Implementation Method 1
silicon typically exhibits a large volume change on lithium insertion, with an increase of up to 300 to 400% in volume possible
Implementation Method 2
lithium-ions move from the negative electrode, or anode, through an electrolyte to the positive electrode, or cathode, during discharge and back during charging
Implementation Method 3
When a battery is connected to an external circuit electrons flow from the anode to the cathode through the external circuit thereby delivering electrical energy to the circuit
Implementation Method 4
A separator prevents shorting between the cathode and anode, whilst still allowing ions to move across the separator between the two half-cells
Data Source
AI summary
The present application concerns a method of manufacturing a lithium-ion cell (12), comprising the steps of: (i) providing a silicon anode (6); (ii) pre-lithiating the silicon anode (6) to form a pre-lithiated silicon anode (1) with a pre-lithiation level of from 1% to 100%; (iii) providing a providing: a separator (2); an electrolyte; and a lithium-ion cathode (3); (iv) forming a lithium-ion cell from the pre-lithiated silicon anode (1), the separator (2) and the lithium-ion cathode (3), wherein the silicon anode (6) comprises a lithium storage material, in which the lithium storage material comprises between 70 and 100 wt. %, preferably 85 and 100 wt. % silicon, with respect to the lithium storage material, and wherein the lithium storage material comprises silicon material with a columnar morphology.