Surface-Mediated Cell Stacks for High Power Density
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Solution Overview
Problem
Conventional lithium-ion batteries and supercapacitors face limitations in energy and power density, with lithium-ion batteries having low power density and long recharge times due to solid-state diffusion, while supercapacitors have low energy density due to solubility limitations of lithium salts in solvents.
Innovation Solution
The development of a surface-mediated cell (SMC) where lithium ions are exchanged between the surfaces of an anode and a cathode, utilizing nano-structured materials with high specific surface areas to facilitate fast and reversible lithium storage, eliminating the need for solid-state diffusion and increasing energy and power density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium-ion batteries use solid-state diffusion for lithium storage, then energy density is improved, but power density deteriorates and recharge time increases
Solution Approach 1:
The invention segments the lithium storage function into two distinct components: a lithium source electrode that provides lithium ions and a lithium storage electrode with high surface area that rapidly stores them. This segmentation allows the lithium source to be optimized for lithium supply while the storage electrode is optimized for rapid surface-mediated storage, eliminating the need for slow solid-state diffusion through thick electrodes and thereby resolving the contradiction between energy density and power density.
Solution Approach 2:
The invention introduces a liquid electrolyte as an intermediary medium that facilitates rapid lithium ion transport between the lithium source electrode and the lithium storage electrode. This liquid-phase transport mechanism is much faster than solid-state diffusion, enabling high power density and rapid recharge while maintaining high energy density through the high surface area storage electrode.
2Power
If supercapacitors use electric double layer for charge storage, then power density is improved, but energy density deteriorates
Solution Approach 1:
The invention employs a porous lithium storage electrode material with extremely high surface area (e.g., activated carbon, graphite, or other carbonaceous materials) that provides numerous surface sites for rapid lithium ion storage. This porous structure maintains the high power density characteristic of supercapacitors by enabling fast surface-mediated storage while dramatically increasing energy density by providing vastly more storage sites than conventional supercapacitor electrodes.
Solution Approach 2:
The invention changes the storage mechanism parameter from electric double layer formation (in supercapacitors) to surface-mediated lithium ion storage. This parameter change allows the system to achieve both high power density (through surface-mediated rapid storage) and high energy density (through high surface area porous materials that can store large amounts of lithium ions).
3Quantity of substance
If lithium-ion batteries use intercalation for lithium storage, then energy density is improved, but recharge time increases
Solution Approach 1:
The invention extracts the slow solid-state diffusion step from the lithium storage process by using a lithium storage electrode with high surface area where lithium ions can be stored directly at the surface through rapid surface-mediated mechanisms. This extraction of the diffusion bottleneck eliminates the time-consuming intercalation process while maintaining high energy density through the high capacity porous storage material.
Solution Approach 2:
The invention segments the battery into a lithium source electrode and a lithium storage electrode, allowing the storage electrode to be optimized for rapid surface-mediated lithium ion uptake. This segmentation enables the storage electrode to rapidly accept lithium ions from the liquid electrolyte without requiring slow solid-state diffusion, thereby dramatically reducing recharge time while maintaining high energy density.
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 high energy density (typically >150 Wh/kg) and power density (no lower than 25 kW/kg), with rapid charge and discharge capabilities, exceeding the performance of both conventional lithium-ion batteries and supercapacitors, and operating over a wide temperature range.
Implementation Method 1
a porous cathode active material having a surface area to capture lithium thereon
Implementation Method 2
the ionic species (cations and anions) in the EDL are formed in the electrolyte near an electrode surface
Implementation Method 3
ionizing the lithium source to release lithium ions into the electrolyte during the first discharge cycle of the device
Implementation Method 4
electrically driving said released lithium ions to said anode active material surfaces
Data Source
AI summary
An energy storage stack of at least two surface-mediated cells (SMCs) internally connected in parallel or in series. The stack includes: (A) At least two SMC cells, each consisting of (i) a cathode comprising a porous cathode current collector and a cathode active material; (ii) a porous anode current collector; and (iii) a porous separator disposed between the cathode and the anode; (B) A lithium-containing electrolyte in physical contact with all the electrodes, wherein the 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 (C) A lithium source. This new-generation energy storage device exhibits the highest power densities of all energy storage devices, much higher than those of all the lithium ion batteries, lithium ion capacitors, and supercapacitors.