Aqueous Solid Polymer Electrolyte for Stable >3 V Li-Ion Cells
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Solution Overview
Problem
Existing rechargeable batteries with high cell voltages (>3.0 V) face challenges due to the instability of non-aqueous electrolytes, which are prone to flammability, toxicity, and require expensive moisture exclusion facilities, while aqueous electrolytes have a narrow electrochemical stability window that cannot support most Li-ion battery chemistries.
Innovation Solution
Development of aqueous solid polymer electrolytes comprising a lithium salt and a polymer, with a molality of lithium salt to water between 1 and 30, and an ionic conductivity of 1 mS/cm to 10 mS/cm at 25°C, enabling stable operation with cell voltages greater than 3 V.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-aqueous electrolytes are used to achieve high cell voltages (>3.0 V), then electrochemical stability is improved, but flammability and toxicity increase
Solution Approach 1:
The patent changes the fundamental parameter of the electrolyte solvent from non-aqueous (organic) to aqueous (water-based), while simultaneously changing the physical state from liquid to solid polymer. This parameter transformation allows the use of water as a safe, non-flammable solvent while maintaining electrochemical stability through the solid polymer matrix and optimized lithium salt concentration (molality 1-30).
Solution Approach 2:
The patent creates a composite electrolyte system combining three components: water (aqueous solvent), lithium salts (electrolyte solute), and polymer matrix (solid structure provider). This composite approach allows the system to exhibit properties of all components - the safety of water, the ionic conductivity of lithium salts, and the structural stability of polymers, resolving the contradiction between stability and safety.
2Object-affected harmful factors
If aqueous electrolytes are used to improve safety, then flammability is reduced, but electrochemical stability window becomes too narrow
Solution Approach 1:
The patent utilizes the phase transition from liquid to solid state by employing a solid polymer electrolyte matrix. This phase change allows the aqueous electrolyte to operate at temperatures where water remains liquid (providing ionic conductivity) while the solid polymer structure prevents electrolyte decomposition and hydrogen evolution, effectively expanding the operational stability window beyond the theoretical 1.23 V limit of liquid aqueous electrolytes.
Solution Approach 2:
The patent changes the physical state parameter from liquid to solid and optimizes the concentration parameter (molality 1-30) to achieve a unique operating regime where aqueous electrolytes can support cell voltages >3.0 V. The solid polymer matrix restricts water molecule mobility, preventing electrochemical decomposition while maintaining ion transport pathways.
3Reliability
If high concentrations of lithium salts are used to achieve adequate ionic conductivity, then conductivity is improved, but viscosity increases
Solution Approach 1:
The patent changes the physical state from liquid to solid polymer, which fundamentally alters the viscosity-concentration relationship. In the solid polymer state, the matrix structure prevents the dramatic viscosity increases that would occur in liquid electrolytes at high salt concentrations. The polymer network provides a rigid framework that maintains low effective viscosity for ion transport while supporting high lithium salt loads (molality 1-30).
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 aqueous solid polymer electrolytes provide enhanced stability, compatibility, and safety, allowing for the use of high concentrations of lithium salts and achieving electrochemical stability windows suitable for Li-ion battery chemistries, thus overcoming the limitations of traditional electrolytes.
Implementation Method 1
at least one lithium salt in water; wherein the molality of the lithium salt to water is between about 1 and about 30, and wherein the ionic conductivity of the electrolyte at 25° C. is between about 1 mS/cm and about 10 mS/cm
Data Source
AI summary
The present invention is directed to aqueous solid polymer electrolytes that comprise a lithium salt and battery cells comprising the same. The present invention is also directed to methods of making the electrolytes and methods of using the electrolytes in batteries and other electrochemical technologies.