High-Voltage Catholyte Composition for Dense Solid-State Cathodes
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Solution Overview
Problem
Existing solid-state lithium batteries face challenges in achieving high energy density and cyclability due to limited stability of catholytes at high voltages, particularly with materials like polyethylene oxide, leading to reduced performance and safety concerns.
Innovation Solution
A high-voltage positive electrode composite comprising lithium cobalt oxide, spinel LiNi0.5Mn1.5O4, lithium nickel manganese cobalt oxide, lithium manganese iron phosphate, or lithium-rich layered oxides, combined with a conductive additive and a catholyte containing lithium salts, polymer binders, room temperature ionic liquids, and plastic crystals, which form a robust interface for improved ionic conductivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large catholyte fraction (30-50 vol%) is used to provide sufficient ionic diffusion, then ionic conductivity is improved, but the volume fraction of cathode active material decreases resulting in low energy density
Solution Approach 1:
The patent changes the chemical composition parameters of the catholyte by incorporating specific additives (LiFSO3 salt, PVdF-HFP polymer, ionic liquids, and nitrile plasticizers) to optimize the balance between ionic conductivity and energy density. This modifies the catholyte's properties to achieve sufficient Li-ion transport with reduced catholyte volume fraction.
Solution Approach 2:
The patent creates a composite catholyte system combining multiple components (lithium salt, polymer binder, ionic liquid, and plastic crystal) that work synergistically. This composite approach enables the catholyte to provide both adequate ionic conductivity and stability, allowing higher CAM volume fractions without sacrificing performance.
2Power
If existing catholytes (such as those containing polyethylene oxide) are used in high voltage composite cathodes, then electrochemical performance is achieved, but stability is limited especially at high temperature such as higher than 40 °C
Solution Approach 1:
The patent modifies the catholyte composition by replacing PEO with a composite system containing PVdF-HFP polymer, LiFSO3 salt, ionic liquids, and nitrile plasticizers. This parameter change significantly improves thermal stability while maintaining electrochemical performance at high temperatures above 40°C and high voltages up to 4.3V.
Solution Approach 2:
The patent replaces the unstable PEO-based catholyte with a more stable composite formulation that has extended operational life and resistance to degradation at high temperatures and voltages, effectively creating a longer-lasting system.
3Quantity of substance
If high loading composite positive electrodes are developed to increase energy density, then volume utilization is improved, but achieving sufficient ionic diffusion and maintaining stability becomes more difficult
Solution Approach 1:
The patent optimizes the catholyte composition parameters to achieve a volume fraction of 20-40% (reduced from conventional 30-50%) while maintaining sufficient ionic diffusion. The specific additives enable this reduction by enhancing Li-ion transport efficiency, allowing higher CAM loading without compromising cyclability.
Solution Approach 2:
The catholyte acts as an intermediary medium that facilitates Li-ion transport between the high-loading CAM and the solid electrolyte. The optimized catholyte composition with specific additives ensures efficient ion diffusion even at high CAM volume fractions, enabling both high energy density and good cyclability.
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 composite electrode achieves high loading and enhanced electrochemical performance, improving energy density and cyclability of lithium-based batteries, especially at high temperatures.
Implementation Method 1
the catholyte should have a high ionic conductivity
Implementation Method 2
a high boiling point solvent having a boiling point of at least 160 °C
Data Source
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AI summary
It is provided positive electrode comprising: (i) a high voltage cathode active material; (ii) a conductive additive; and (iii) a high voltage-stable catholyte comprising: a lithium salt, a polymer binder which is a PVdF co-polymer, a room temperature ionic liquid, a plastic crystal, and, optionally, a high boiling point solvent; wherein the positive electrode is characterized by having a density from 2.3 g/cm3 to 3.6 g/cm3. It is also provided a process for the preparation of the positive electrode, as well as a battery comprising the positive electrode and an article of manufacture comprising the battery.