Multilayer Li-Ion Electrodes to Mitigate Polarization Gradients
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Solution Overview
Problem
Conventional lithium-ion battery electrodes face challenges with excessive polarization during charging and discharging, leading to low capacity utilization and safety risks due to natural gradient fields, which impairs performance and increases the risk of lithium plating on the anode surface.
Innovation Solution
The electrodes are designed with multiple layers of active materials having different lithiation energies and solid-state diffusion coefficients, with materials requiring less energy to lithiate closer to the current collector and those requiring more energy closer to the separator, optimizing the lithiation process and mitigating gradient fields by strategically orienting active materials within the electrode bulk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional single-layer electrodes are used, then the electrode structure is simple, but excessive polarization occurs during charging and discharging leading to low capacity utilization and safety risks
Solution Approach 1:
The electrode is divided into multiple layers (first layer, second layer, third layer) with different active materials having different lithiation energies. This segmentation allows each layer to handle different aspects of the lithiation process, reducing overall polarization and improving capacity utilization while maintaining a manageable structured approach.
Solution Approach 2:
Different regions of the electrode (different layers) are assigned different active materials with specific properties tailored to their location. The first layer uses materials with lower lithiation energy near the current collector, while subsequent layers use materials with progressively higher lithiation energies, optimizing local conditions for ion transport and reaction kinetics throughout the electrode bulk.
2Reliability
If natural gradient fields are present in conventional electrodes, then the electrode structure is uniform, but lithium plating occurs on the anode surface increasing safety risks
Solution Approach 1:
The electrode is segmented into multiple layers with progressively different lithiation energy characteristics. This prevents the formation of strong natural gradient fields that cause lithium plating by distributing the lithiation energy requirements across layers, ensuring more uniform lithium ion distribution and reducing safety risks.
Solution Approach 2:
The lithiation energy parameter is systematically varied across different layers of the electrode. By changing this parameter from the first layer to subsequent layers, the electrode optimizes lithium ion acceptance at different depths, preventing excessive polarization and lithium plating while maintaining structural organization.
3Productivity
If materials requiring more energy to lithiate are placed closer to the current collector, then lithiation efficiency improves, but gradient fields increase causing polarization
Solution Approach 1:
Instead of placing high-energy materials near the current collector, the invention inverts this arrangement by placing low lithiation energy materials in the first layer near the current collector and progressively higher energy materials in subsequent layers. This inverted gradient reduces polarization and natural gradient field formation while maintaining efficient lithiation rates.
Solution Approach 2:
The lithiation energy parameter is systematically changed across layers in a controlled manner, with the first layer having lower lithiation energy and subsequent layers having progressively higher energies. This parameter progression optimizes the balance between lithiation rate and polarization reduction.
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
This design enhances the rate capabilities of lithium-ion batteries by improving lithiation properties, increasing power density, and preventing unwanted lithium plating, thus enhancing overall battery performance and safety.
Implementation Method 1
a first layer adjacent the first current collector substrate and including a plurality of first active material particles adhered together by a first binder, the first active material particles comprising a mixture of graphitic carbon and hard carbon configured to have a first free energy to lithiate per mole; and a second layer adjacent the liquid-permeable separator and including a plurality of second active material particles configured to have a second free energy to lithiate per mole
Data Source
AI summary
Electrochemical cells of the present disclosure may include one or more multilayered electrodes. Each multilayered electrode may be configured such that active materials of the layer closest to the current collector have a lower energy to lithiate per mole, a higher energy to delithiate per mole, a different solid state diffusivity, and/or a different average particle size. This arrangement counteracts, for example, natural gradient fields and undesirable polarization found in standard lithium-ion batteries.