Semi-solid Electrodes for High Rate Capability Batteries
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Solution Overview
Problem
Conventional battery manufacturing methods result in electrodes with limited thickness, lower capacity, lower energy density, and higher inactive component ratios, making them costly and inefficient, while also facing challenges in achieving both high rate capability and charge capacity simultaneously.
Innovation Solution
The development of semi-solid electrodes with a suspension of 35% to 75% active material and 0.5% to 8% conductive material in a non-aqueous liquid electrolyte, allowing for thicker electrodes (250 µm to 2,000 µm) with reduced tortuosity and increased electronic conductivity, thereby enhancing charge capacity and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional solid electrodes with binders are used, then manufacturing process is established, but electrode thickness is limited to less than 100 μm and tortuosity increases
Solution Approach 1:
The patent removes the binder component from the electrode formulation entirely, extracting the problematic element that caused tortuosity and thickness limitations. The binderless semi-solid electrode composition eliminates the need for polymeric binders that increased tortuosity, allowing for thicker electrodes with improved ionic conductivity and reduced structural complexity.
Solution Approach 2:
The patent changes the physical state parameter of the electrode from solid to semi-solid, transforming the electrode composition into a slurry or paste form. This parameter change enables thicker electrode construction (250-2000 μm) while maintaining electrochemical performance, as the semi-solid state allows for better ion transport pathways and reduced tortuosity compared to conventional solid electrodes.
2Quantity of substance
If electrode thickness is increased to improve capacity, then charge capacity increases, but rate capability decreases due to higher tortuosity
Solution Approach 1:
The patent changes the electrode from solid to semi-solid state, which fundamentally alters the transport properties. The semi-solid electrode maintains low tortuosity even at increased thickness (250-2000 μm), enabling both high charge capacity and high rate capability. The slurry or paste formulation creates more direct ion transport pathways compared to solid electrodes.
Solution Approach 2:
The patent uses composite semi-solid electrode materials consisting of active material particles suspended in a liquid or gel electrolyte matrix. This composite structure combines the high capacity benefits of thick electrodes with the low tortuosity characteristics of liquid electrolytes, achieving both high charge capacity and high rate capability simultaneously.
3Strength
If binders are added to solid electrode formulations, then electrode integrity is maintained, but ionic conductivity decreases and tortuosity increases
Solution Approach 1:
The patent removes binders from the electrode formulation, eliminating the source of increased tortuosity and reduced ionic conductivity. The binderless semi-solid electrode maintains integrity through the viscous nature of the slurry or paste formulation and the interparticle contacts in the semi-solid matrix, without requiring polymeric binder materials.
Solution Approach 2:
The patent employs a liquid or gel electrolyte matrix in the semi-solid electrode that provides ion transport pathways similar to hydraulic systems. The liquid/gel phase fills the spaces between active material particles, creating continuous ionic conduction paths that bypass the need for solid binders and significantly improve ionic conductivity while maintaining electrode structural integrity.
4Ease of manufacture
If conventional coating and calendering methods are used, then manufacturing is established, but manufacturing cost increases and electrode thickness is limited
Solution Approach 1:
The patent changes the electrode formulation from solid to semi-solid, which enables alternative manufacturing approaches such as direct casting or extrusion of the slurry or paste form. These methods eliminate the need for complex coating and calendering equipment, reducing manufacturing process complexity and cost while enabling thicker electrode production.
Solution Approach 2:
The semi-solid slurry or paste formulation can be processed using pumping and casting techniques similar to hydraulic systems, replacing the mechanical coating and calendering processes. This approach simplifies manufacturing equipment requirements and enables more straightforward production of thick electrodes without the complex multi-step processes needed for solid electrodes.
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
Semi-solid electrodes enable superior rate capability and charge capacity, reduce manufacturing complexity and costs, and increase the active-to-inactive material ratio, leading to higher energy density and commercial appeal.
Implementation Method 1
a suspension of about 35% to about 75% by volume of an active material and about 0.5% to about 8% by volume of a conductive material in a non-aqueous liquid electrolyte
Data Source
Figure 1
Figure 2A~2C
Figure 3A~3C
AI summary
Embodiments described herein relate generally to electrochemical cells having high rate capability, and more particularly to devices, systems and methods of producing high capacity and high rate capability batteries having relatively thick semi-solid electrodes. In some embodiments, an electrochemical cell includes an anode and a semi-solid cathode. The semi-solid cathode includes a suspension of an active material of about 35% to about 75% by volume of an active material and about 0.5% to about 8% by volume of a conductive material in a nonaqueous liquid electrolyte. An ion-permeable membrane is disposed between the anode and the semi-solid cathode. The semi-solid cathode has a thickness of about 250 µm to about 2,000 µm, and the electrochemical cell has an area specific capacity of at least about 7 mAh/cm2 at a C-rate of C/4. In some embodiments, the semi-solid cathode slurry has a mixing index of at least about 0.9.