Surface-Mediated Cell for High Power and Energy Density
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Solution Overview
Problem
Conventional energy storage devices, such as supercapacitors and lithium-ion batteries, face limitations in energy density and power density, with supercapacitors offering high power density but low energy storage and lithium-ion batteries providing high energy density but low power density, making them unsuitable for applications requiring both high energy and power.
Innovation Solution
The development of a surface-mediated cell (SMC) that facilitates the exchange of lithium ions between massive anode and cathode surfaces, eliminating the need for solid-state diffusion and utilizing high-specific-surface-area materials like graphene to achieve rapid charge and discharge cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If supercapacitors use porous electrodes to create large surface area for diffuse electric double layer charges, then power density is improved (3,000-8,000 W/Kg), but energy density deteriorates (5-8 Wh/kg)
Solution Approach 1:
The patent changes the fundamental operating parameters by using surface-mediated lithium ion exchange instead of diffuse electric double layer formation. This allows the device to operate at higher voltages (2.5-4.2V vs 0-2.7V for supercapacitors) while maintaining fast kinetics through surface-level ion exchange, achieving both high power density (100 kW/kg) and high energy density (100-200 Wh/kg) simultaneously
Solution Approach 2:
The patent introduces lithium ions as an intermediary species that mediates the charge transfer between electrodes. Instead of relying solely on pre-existing ions in the electrolyte forming diffuse double layers, lithium ions are actively exchanged between the porous electrodes and electrolyte, enabling both high capacity storage and fast kinetics through surface-mediated exchange processes
2Quantity of substance
If lithium-ion batteries use bulk intercalation of lithium ions between anode and cathode, then energy density is improved (100-180 Wh/kg), but power density deteriorates (100-500 W/Kg)
Solution Approach 1:
The patent transitions from three-dimensional bulk intercalation to two-dimensional surface-mediated exchange. By confining lithium ion exchange to the surface layer of porous electrodes rather than requiring diffusion through the entire bulk material, the device achieves both high energy capacity (through porous structure volume) and high power density (through surface-level fast kinetics), reaching 100-200 Wh/kg and 100 kW/kg respectively
Solution Approach 2:
The patent segments the electrode structure into porous frameworks with high surface area, creating numerous discrete surface sites for parallel lithium ion exchange. This segmentation allows simultaneous charge transfer at many locations, dramatically increasing power density while the overall porous structure maintains high energy capacity, achieving 100 kW/kg power density with 100-200 Wh/kg energy density
3Reliability
If supercapacitors form electric double layers without chemical reactions, then cycle life is improved (extraordinarily high), but energy density deteriorates (5-8 Wh/kg)
Solution Approach 1:
The patent replaces the purely physical electric double layer formation mechanism with a surface-mediated chemical exchange mechanism. Lithium ions undergo reversible exchange reactions at the electrode surfaces, forming stable surface complexes that provide both high energy density (100-200 Wh/kg) and excellent cycle life through the stability of surface-mediated reaction pathways, eliminating the need for diffuse ion distribution in the electrolyte
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 SMC achieves a high energy density of 100-200 Wh/kg and a maximum power density of 100 kW/kg, combining the benefits of both energy and power density, with a unique electrochemical mechanism that surpasses conventional devices in cycle life and operating temperature range.
Implementation Method 1
a cathode comprising a cathode active material having a surface area to capture or store lithium thereon
Implementation Method 2
an anode comprising either an anode current collector alone or a combination of an anode current collector and an anode active material having a surface area to capture or store lithium thereon
Implementation Method 3
a lithium-containing electrolyte in physical contact with the two electrodes, wherein the anode active material and/or the cathode active material has a specific surface area of no less than 100 m2/g being in direct physical contact with the electrolyte to receive lithium ions therefrom or to provide lithium ions thereto
Data Source
AI summary
A surface-mediated cell (SMC) comprising: (a) a cathode comprising a carbon-based cathode active material having a surface area to capture or store lithium thereon; (b) an anode comprising an anode current collector alone, or combined anode current collector and anode active material; (c) a porous separator disposed between the anode and the cathode; (d) a lithium-containing electrolyte, wherein the anode and/or cathode active material has a specific surface area no less than 100 m2/g in direct physical contact with the electrolyte to receive lithium ions therefrom or to provide lithium ions thereto; and (e) a lithium source disposed in at least one of the two electrodes when the cell is made, and the cell has an open-circuit voltage (OCV) of at least 0.8 volts; wherein the cell operates between a lower voltage limit lower than the OCV and an upper limit of between 3.8 and 4.5 volts.