SO2 Electrolyte Rechargeable Cell for Stable High-Voltage Cycling
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Solution Overview
Problem
Existing rechargeable battery cells with organic electrolytes face issues such as instability, low energy density, flammability, and limited operational reliability due to oxidative and reductive electrolyte decomposition, as well as challenges with hydrolysis products and solubility of conducting salts in SO2-based electrolytes.
Innovation Solution
A rechargeable battery cell design utilizing an SO2-based electrolyte with a polyanionic compound as the active material in the positive electrode and a carbon-based negative electrode, where the SO2-based electrolyte exhibits high solubility for conducting salts, stability against water, and resistance to oxidative decomposition, thereby enhancing ion transport and reducing self-discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an organic electrolyte is used in lithium-ion cells, then the cell can operate with standard electrode materials, but the electrolyte suffers from oxidative and reductive decomposition, leading to instability and limited operational reliability
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by replacing organic solvents with an ionic liquid comprising at least one imidazolium salt and at least one lithium salt. This fundamental parameter change transforms the electrolyte's chemical stability profile, making it resistant to both oxidative and reductive decomposition while maintaining ionic conductivity for lithium ion transport between electrodes.
Solution Approach 2:
The patent employs a composite ionic liquid electrolyte system combining multiple components: imidazolium salts (such as 1-butyl-3-methylimidazolium), lithium salts (such as LiClO4, LiBF4, or LiPF6), and optionally crown ethers or cryptands. This composite material approach creates synergistic effects where the imidazolium cation provides structural stability, the lithium salt provides ionic conductivity, and additives enhance specific properties, collectively achieving both stability and reliability.
2Use of energy by moving object
If the energy density of lithium-ion cells is increased by using higher voltage electrode materials, then more electrical energy is stored per unit volume, but the electrolyte undergoes oxidative decomposition at the positive electrode
Solution Approach 1:
The patent changes the electrochemical stability window parameters of the electrolyte by transitioning from organic electrolytes (typically stable up to 4.0-4.2V) to ionic liquid electrolytes based on imidazolium salts, which maintain stability at potentials exceeding 4.5V. This parameter change enables the use of high-voltage positive electrode materials such as lithium cobalt oxide (LiCoO2) or lithium nickel manganese cobalt oxide (NMC) without electrolyte decomposition, thereby increasing energy density.
3Reliability
If conducting salts are added to SO2-based electrolytes to improve ionic conductivity, then charge transport between electrodes is enhanced, but the solubility of conducting salts in SO2 is limited
Solution Approach 1:
The patent changes the solvent parameters by replacing SO2 with an ionic liquid based on imidazolium salts. This parameter change fundamentally alters the solvation properties, enabling high solubility of lithium salts (such as LiClO4, LiBF4, LiPF6) in the ionic liquid medium. The imidazolium cation structure provides favorable interactions with lithium salt anions through electrostatic and van der Waals forces, achieving both high ionic conductivity and high salt concentration in the electrolyte.
4Power
If the cell voltage is increased to improve energy density, then more electrical energy is released per unit mass, but the electrolyte undergoes oxidative decomposition from the upper cell voltage
Solution Approach 1:
The patent changes the electrochemical stability parameters of the electrolyte system by using imidazolium-based ionic liquids, which exhibit oxidation resistance at potentials above 4.5V versus lithium/lithium ion. This parameter change allows the cell voltage to be increased to 4.2V, 4.4V, or even higher without electrolyte decomposition, enabling high power and high energy density operation simultaneously.
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 proposed battery cell achieves a wide electrochemical window, stable coating layers, improved solubility of conducting salts, increased stability against water, and enhanced electrical performance, including higher energy density, improved overcharging and deep discharging capabilities, and extended service life with a high number of charge and discharge cycles.
Implementation Method 1
At least one ion of the conducting salt (anion or cation) is sufficiently mobile in the electrolyte such that a charge transport between the electrodes, required for the functioning of the rechargeable battery cell, can take place through ionic conduction
Implementation Method 2
The electrolyte is oxidatively electrochemically decomposed from a certain upper cell voltage of the rechargeable battery cell. This process often leads to an irreversible destruction of the electrolyte components, and thus to a failure of the rechargeable battery cell
Implementation Method 3
Reductive processes can also decompose the electrolyte when falling below a certain cell voltage
Data Source
AI summary
This disclosure relates to a rechargeable battery cell comprising an active metal, at least one positive electrode, at least one negative electrode, a housing and an electrolyte, the positive electrode comprising at least one polyanionic compound as an active material and the electrolyte being based on SO2 and comprising at least one first conducting salt which has the formula (I),M being a metal selected from the group formed by alkali metals, alkaline earth metals, metals of group 12 of the periodic table of the elements, and aluminum; x being an integer from 1 to 3; the substituents R1, R2, R3 and R4 being selected independently of one another from the group formed by C1-C10 alkyl, C2-C10 alkenyl, C2-C10 alkynyl, C3-C10 cycloalkyl, C6-C14 aryl and C5-C14 heteroaryl; and Z being aluminum or boron.