Organic Li-Bromine Battery Electrolyte for Stable Two-Electron Redox
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Solution Overview
Problem
Existing lithium-bromine batteries face challenges due to the thermodynamic instability of bromine ions in positive valence states in current electrolytes and the unsuitability of elemental Br2 for electrodes due to its fluidity and volatility, limiting their capacity and energy density.
Innovation Solution
A high-performance organic lithium-bromine battery is developed using a bromide-based cathode, an anode, and an organic electrolyte with chloride ions-containing additives, which triggers a conversion of positively charged bromine ions, facilitating an additional electron transfer and enhancing capacity and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional single-electron conversion mode is used in lithium-bromine batteries, then voltage and capacity can be achieved, but energy density remains limited and performance improvements are constrained
Solution Approach 1:
The patent changes the electron transfer parameter from single-electron to two-electron redox chemistry. By utilizing bromide ions (Br-) that can transfer two electrons instead of the conventional single-electron transfer, the battery achieves doubled capacity (653 mAh g-1 vs. 335 mAh g-1) and higher energy density (2180 Wh kg-1Br), directly resolving the energy density limitation while maintaining manageable system complexity
Solution Approach 2:
The patent employs a composite electrolyte system combining organic electrolytes with specific additives (LiClO4, LiBF4, LiPF6) to enable stable two-electron redox chemistry. This composite approach creates a chemically stable environment that supports the complex Br-/Br0/Br+ redox couple while maintaining overall system manageability and performance
2Quantity of substance
If bromide-based cathode with two-electron redox chemistry is implemented, then capacity and energy density are significantly enhanced, but thermodynamic instability of bromine ions in positive valence states occurs in conventional electrolytes
Solution Approach 1:
The patent introduces specific electrolyte additives (LiClO4, LiBF4, LiPF6) as intermediaries that mediate between the bromide cathode and the organic electrolyte. These additives create a stable chemical environment that prevents decomposition of bromine ions in positive valence states, enabling the Br-/Br0/Br+ redox couple to operate reliably while achieving high capacity of 653 mAh g-1
Solution Approach 2:
The patent changes the electrolyte composition parameters by using organic electrolytes with specific lithium salt additives instead of conventional aqueous electrolytes. This parameter change creates a chemically stable environment with appropriate solvation properties that supports the thermodynamically challenging two-electron redox chemistry while maintaining electrolyte reliability over 1000 cycles
3Ease of manufacture
If elemental Br2 is used in non-flow batteries, then bromine redox chemistry can be achieved, but fluidity and volatility make it unsuitable for electrodes
Solution Approach 1:
The patent applies local quality by using bromide ions (Br-) in a fixed solid-state cathode structure rather than elemental Br2. This local modification confines the bromine in a stable crystalline or amorphous matrix, eliminating fluidity and volatility issues while maintaining the desired redox activity at the electrode sites, thereby enabling easy electrode fabrication with stable composition
Solution Approach 2:
The patent uses bromide salts (such as NaBr, KBr, or organic ammonium bromides) as stable solid-state copies that replicate the redox functionality of elemental bromine without its harmful physical properties. These bromide compounds serve as stable proxies that can be easily incorporated into electrode structures while providing the necessary Br-/Br0/Br+ redox chemistry
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 battery achieves a capacity of at least 600 mAh g−1 and an energy density of at least 2000 Wh kg−1Br, with a prolonged lifetime of up to 1000 cycles and negligible capacity attenuation, significantly surpassing the performance of conventional lithium-bromine batteries.
Implementation Method 1
The chloride ions within the organic electrolyte trigger a conversion of positively charged bromine ions, facilitating an additional electron transfer
Data Source
AI summary
The present invention provides a high-performance organic lithium-bromine battery enabled by two-electron redox chemistry. The battery includes a bromide-based cathode, an anode, an organic electrolyte disposed in a space between the bromide-based cathode and the anode, featuring an organic solvent with chloride ions-containing additives, and a separator positioned between the bromide-based cathode and anode. The chloride ions within the organic electrolyte trigger a conversion of positively charged bromine ions, facilitating an additional electron transfer and resulting in a capacity of at least 600 mAh g−1, and elevates an output plateau to 3.8 V, thereby achieving an energy density of at least 2000 Wh kg−1Br.