Lithium-Ion Battery Electrolyte Stability at High Voltage
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Solution Overview
Problem
Lithium ion secondary batteries with high energy density suffer from capacity decrease due to the decomposition of electrolytic liquids when operating at higher voltages, such as 4.5 V, leading to reduced performance over charge/discharge cycles.
Innovation Solution
Incorporating a fluorine-containing ether compound, specifically 1,1,2,3,3,3-hexafluoropropyl difluoromethyl ether, into the electrolytic liquid, combined with a lithium-iron-manganese complex oxide positive electrode having a layered rock salt structure, to enhance solubility and stability, thereby suppressing capacity loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a positive electrode having a high electrical potential is used to increase energy density, then the voltage increases to 4.5 V or more, but the electrolytic liquid decomposes leading to deterioration of battery performance
Solution Approach 1:
The invention changes the chemical composition parameters of the electrolytic liquid by introducing a specific fluorine-containing ether compound with the formula CF3CF2CH(OCH2F)2. This compound has unique molecular structure parameters (fluorine substitution pattern, ether linkage) that enable it to withstand high voltage conditions. The parameter change transforms the electrolyte from one that decomposes at 4.5V to one that remains stable, allowing the high-potential positive electrode to function reliably.
Solution Approach 2:
The fluorine-containing ether compound acts as an intermediary substance between the high-potential positive electrode and the conventional electrolytic liquid. It mediates the interaction by forming a protective interface layer that prevents direct contact and decomposition reactions between the electrolyte and the high-voltage electrode, thus protecting the battery performance while enabling high energy density operation.
2Power
If conventional fluorine-containing ether compounds are used in the electrolytic liquid, then the battery operates at high voltage, but the capacity decreases drastically through charge/discharge cycles
Solution Approach 1:
The invention applies local quality by designing a fluorine-containing ether compound with specific localized functional groups: trifluoromethyl groups (CF3) for electrochemical stability, difluoromethoxy groups (OCH2F) for solubility and film-forming capability. This localized functional distribution creates different regions of chemical activity within the molecule, enabling it to simultaneously provide high-voltage stability and long cycle life by forming a durable solid electrolyte interface (SEI) layer.
Solution Approach 2:
The electrolytic liquid becomes a composite system combining conventional carbonate solvents with the specifically designed fluorine-containing ether compound. This composite electrolyte leverages the advantages of both components: the carbonate solvents provide good ionic conductivity and solubility, while the fluorine-containing ether compound provides high-voltage stability and cycle life enhancement through protective film formation.
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 effectively maintains battery capacity over repeated charge/discharge cycles at higher voltages, extending the battery's lifespan as a high energy density secondary battery.
Implementation Method 1
the fluorine-containing ether compound exhibits excellent solubility in a non-aqueous solvent
Implementation Method 2
a positive electrode active material being a lithium-iron-manganese complex oxide having a layered rock salt structure
Data Source
AI summary
A lithium ion secondary battery comprising: a positive electrode comprising a positive electrode active material; a negative electrode comprised mainly of a material capable of storing and releasing lithium ions; and an electrolytic liquid,the positive electrode active material being a lithium-iron-manganese complex oxide having a layered rock salt structure and represented by a chemical formula:LixFesM1(z-s)M2yO2-δwherein 1.05≦x≦1.32, 0.06≦s≦0.50, 0.06≦z≦0.50, 0.33≦y≦0.63, and 0≦δ≦0.80; M1 represents a metal selected from the group consisting of Co, Ni, Mn and a mixture thereof; and M2 represents a metal selected from the group consisting of Mn, Ti, Zr and a mixture thereof,the electrolytic liquid comprising 1,1,2,3,3,3-hexafluoropropyl difluoromethyl ether represented by the following formula (1):