Sodium Ion Battery Electrolyte Solvent Mixture
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Solution Overview
Problem
Conventional sodium-ion secondary batteries face challenges in using room temperature due to solid ethylene carbonate as a solvent and suffer from poor conductivity and volumetric changes in carbon materials, leading to battery performance decline.
Innovation Solution
Employing a mixed solvent of saturated cyclic carbonate and linear carbonate, such as propylene carbonate, with hard carbon as the anode active material to enhance charge/discharge efficiency and maintain performance at room temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ethylene carbonate is used as the nonaqueous solvent, then the cycle characteristics of the battery are improved, but the battery cannot be used at room temperature because ethylene carbonate is solid at room temperature
Solution Approach 1:
The patent combines ethylene carbonate (solid at room temperature, good cycle characteristics) with diethyl carbonate (liquid at room temperature, low viscosity) in a mixed solvent system. This merging allows the battery to maintain good cycle characteristics from ethylene carbonate while achieving room temperature operability from diethyl carbonate, resolving the contradiction between cycle performance and operating temperature
Solution Approach 2:
The patent changes the physical state parameters of the solvent system by using a mixture rather than pure ethylene carbonate. The mixed solvent system has different melting and viscosity characteristics compared to pure ethylene carbonate, enabling the battery to operate at room temperature while retaining the electrochemical benefits of ethylene carbonate
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 significantly reduces battery performance decline and allows sodium-ion secondary batteries to operate effectively at room temperature with improved cycle characteristics and discharge capacity retention.
Implementation Method 1
carry out charge/discharge by causing lithium ions to migrate between the cathode and anode
Implementation Method 2
a nonaqueous electrolyte solution in which an electrolyte salt is dissolved in a nonaqueous solvent
Implementation Method 3
sodium can be stored and released in the anode
Data Source
AI summary
Disclosed is a sodium-ion secondary battery having excellent charge and discharge efficiencies as well as excellent charge and discharge characteristics, wherein charging and discharging can be repeated without causing problems such as deterioration in battery performance. Specifically disclosed is a sodium ion secondary battery which is provided with a positive electrode, a negative electrode having a negative electrode active material, and a nonaqueous electrolyte solution containing a nonaqueous solvent. The nonaqueous solvent is substantially composed of a saturated cyclic carbonate (excluding the use of ethylene carbonate by itself), or a mixed solvent of a saturated cyclic carbonate and a chain carbonate, and a hard carbon is used as the negative electrode active material. It is preferable that the nonaqueous solvent used for the sodium-ion secondary battery is substantially composed of propylene carbonate, a mixed solvent of ethylene carbonate and diethyl carbonate, or a mixed solvent of ethylene carbonate and propylene carbonate.