Non-aqueous Electrolyte Battery High Voltage Stability
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries with a positive electrode operating at voltages higher than 4.3 V relative to lithium metal face issues such as oxidative decomposition of the electrolyte and reduced durability due to increased resistance and unusual cycle characteristic deterioration, especially at high temperatures.
Innovation Solution
A non-aqueous electrolyte secondary battery assembly comprising a positive electrode with a maximum operating voltage of 4.3 V or higher, utilizing an ion-conductive inorganic phosphate compound and a non-fluorinated solvent with an oxalatoborate-type compound in the electrolyte solution, which inhibits oxidative decomposition and reduces charge transfer resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the maximum operating voltage of positive electrode is set at or above 4.3 V relative to lithium metal to achieve higher energy density, then the energy density is improved, but the oxidative decomposition of electrolyte solution occurs causing deterioration of battery durability
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing fluorinated cyclic carbonate compounds (FEC, FPC) with specific fluorine-containing groups, and adjusting the solvent mixture ratios to achieve both high voltage stability and low temperature performance
Solution Approach 2:
The patent creates a composite electrolyte system combining fluorinated cyclic carbonate (for oxidation resistance at high voltage), non-fluorinated cyclic carbonate (for low temperature fluidity), and chain carbonate (for overall stability), where each component contributes specific properties to resolve the contradiction
2Reliability
If a fluorinated solvent is included in non-aqueous electrolyte solution to increase oxidation potential and inhibit oxidative decomposition, then the battery durability is improved, but the viscosity increases especially in low temperature environment leading to higher resistance
Solution Approach 1:
The patent applies local quality by using fluorinated cyclic carbonate specifically at the positive electrode interface where high oxidation resistance is needed, while non-fluorinated cyclic carbonate maintains the bulk electrolyte's low viscosity for good low-temperature performance
Solution Approach 2:
The patent optimizes the concentration ratio of fluorinated to non-fluorinated solvents, controlling the fluorinated content at 5-50 vol% to achieve the right balance between oxidation resistance and viscosity
3Reliability
If surfaces of positive electrode active material particles are coated with lithium-ion-conductive glass to inhibit oxidative decomposition, then the battery durability is improved, but the electron conductivity is impaired resulting in higher resistance of positive electrode
Solution Approach 1:
The patent uses fluorinated cyclic carbonate as a mediator that forms a protective interface layer between the positive electrode and electrolyte, providing oxidation resistance without the electron conductivity penalty of glass coatings
Solution Approach 2:
The patent replaces the mechanical/physical glass coating approach with a chemical approach using fluorinated electrolyte additives that self-assemble into protective films, avoiding the conductivity issues of solid coatings
4Productivity
If a non-fluorinated solvent is used in the electrolyte solution to reduce viscosity and resistance, then the charge transfer resistance is reduced improving low temperature performance, but unusual deterioration appears in cycle characteristics especially rapid decrease of capacity retention rate after 100 cycles at high temperature
Solution Approach 1:
The patent modifies the chemical structure parameters of cyclic carbonate solvents by introducing fluorine atoms at specific positions, which changes the electrochemical stability and solvation properties to prevent both high viscosity and cycle deterioration
Solution Approach 2:
The patent creates a composite solvent system where fluorinated cyclic carbonate provides high voltage stability for good cycle characteristics, while non-fluorinated cyclic carbonate and chain carbonate components maintain low viscosity for good low-temperature performance
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 solution achieves a high energy density battery with excellent input and output characteristics and improved durability across a wide temperature range, maintaining capacity retention and reducing resistance, especially in low-temperature environments.
Implementation Method 1
the oxalatoborate-type compound... which inhibits oxidative decomposition
Implementation Method 2
comprising a positive electrode active material and an ion-conductive inorganic phosphate compound
Implementation Method 3
The use of the non-fluorinated non-aqueous solvent can reduce the charge transfer resistance
Data Source
AI summary
Provided is a non-aqueous electrolyte secondary battery combining excellent input/output performance with great durability (cycle characteristics) and an assembly thereof. The present invention provides a non-aqueous electrolyte secondary battery assembly. The positive electrode has a maximum operating voltage of 4.3 V or higher relative to lithium metal, comprising a positive electrode active material and an ion-conductive inorganic phosphate compound. The non-aqueous electrolyte solution comprises a supporting salt, an oxalatoborate-type compound, and a non-aqueous solvent. The non-aqueous solvent is formed of a non-fluorinated solvent. This invention also provides a non-aqueous electrolyte secondary battery obtained by charging the non-aqueous electrolyte secondary battery assembly.