Cathode Redox-Active Materials for Battery Pre-Lithiation
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Solution Overview
Problem
Current battery technology fails to meet the energy density requirements for all-electric vehicles, particularly due to lithium loss during the formation of the solid electrolyte interphase in batteries, which limits their performance and efficiency.
Innovation Solution
Incorporating redox active species into or onto the cathode of electrochemical cells, such as small organic molecules or polymeric materials, which have low solubility in the electrolyte, to facilitate pre-lithiation or pre-sodiation, thereby enhancing energy density and mitigating lithium loss by providing a pathway for successful charge and discharge processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional electrolytes are used in batteries, then lithium loss occurs during solid electrolyte interphase formation, but using redox active species with low solubility in the electrolyte can mitigate this loss
Solution Approach 1:
The redox active species are incorporated into the cathode structure before battery operation to perform pre-lithiation during the first charge cycle. This preliminary action compensates for lithium loss that would otherwise occur during solid electrolyte interphase formation, ensuring sufficient lithium remains for subsequent cycling performance.
Solution Approach 2:
The redox active species act as an intermediary material between the cathode and electrolyte, facilitating controlled lithium ion transfer while suppressing harmful shuttling effects. These species mediate the interaction between lithium and the electrolyte, enabling pre-lithiation without the negative effects of conventional electrolyte-based pre-lithiation methods.
2Object-generated harmful factors
If redox active species are incorporated into the cathode, then shuttling effects are suppressed, but the cathode structure becomes more complex
Solution Approach 1:
The redox active species are merged with the cathode active material into a single integrated cathode structure. Rather than adding separate components, the redox species are combined with the cathode material at the molecular level, suppressing shuttling effects while maintaining structural simplicity and avoiding additional complex subsystems.
3Use of energy by moving object
If pre-lithiation is performed to compensate for lithium loss, then energy density improves, but side reactions may occur
Solution Approach 1:
The solubility parameter of the redox active species is specifically optimized to be low in the electrolyte, which fundamentally changes the behavior compared to conventional soluble pre-lithiation agents. This parameter change suppresses side reactions by preventing the dissolution and shuttling of redox species, while still enabling effective pre-lithiation to achieve 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 use of redox active species in the cathode of electrochemical cells suppresses shuttling effects and side reactions, leading to improved cycling performance and increased specific capacity, effectively addressing the energy density limitations of existing battery technologies.
Implementation Method 1
Upon oxidation, the redox active species releases lithium cations that dissolve in the electrolyte
Implementation Method 2
the dissolution of the oxidized redox active species is suppressed by the weakly solvating electrolyte
Data Source
AI summary
An electrochemical cell includes an anode that includes silicon, a conductive carbon, a lithium titanate, lithium metal, or a combination of any two or more thereof; a separator; a cathode having a cathode active material and a redox active species either mixed into the cathode or coated onto the cathode; and an electrolyte that includes a salt; and an aprotic solvent comprising a fluorinated ether solvent, a carbonate solvent, or a mixture thereof, with the proviso that the redox active species has substantially no solubility in the electrolyte. The redox active species may be a redox active organic compound or polymer.