Lithium Secondary Battery Electrolyte for Low-Resistance Cathode Films
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Solution Overview
Problem
Lithium secondary batteries face issues with deteriorating output characteristics and cycle life due to side reactions between the cathode active material and electrolyte, necessitating improved electrochemical performance.
Innovation Solution
A lithium secondary battery design incorporating a cathode with lithium transition metal oxide, an electrolyte containing lithium nitrate, carbonate, and ether solvents, with a controlled lithium nitrate dissolution ratio, forms a low-resistance film on the electrode surface, reducing internal resistance and enhancing capacity and cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte composition is used, then basic battery operation is maintained, but output characteristics and cycle life deteriorate due to side reactions between cathode active material and electrolyte
Solution Approach 1:
Lithium nitrate is introduced as an intermediary substance that mediates the interaction between the cathode active material and the electrolyte. It forms a protective interface layer that prevents direct harmful contact and side reactions between the cathode material and electrolyte, thereby improving cycle life and output characteristics while maintaining basic battery operation
Solution Approach 2:
The electrolyte composition parameters are changed by adding lithium nitrate at specific concentrations (0.01 to 0.07 as defined by Equation 1) and adjusting the ratio of ether solvent (1 to 10 volume%). These parameter changes optimize the electrolyte's interaction with the cathode material, reducing side reactions and improving reliability
2Productivity
If high current density is applied, then fast charging capability is improved, but internal resistance increases and performance deteriorates
Solution Approach 1:
Lithium nitrate acts as an intermediary that facilitates efficient ion transport at the cathode-electrolyte interface. The protective layer it forms maintains low resistance even under high current density conditions, enabling fast charging while preventing performance deterioration and excessive internal resistance buildup
3Reliability
If ether solvent content is increased to dissolve lithium nitrate, then low-resistance film formation is improved, but electrolyte composition stability may be affected
Solution Approach 1:
The electrolyte composition parameters are precisely optimized by controlling the ether solvent content (1 to 10 volume%) and lithium nitrate concentration (following Equation 1). This balanced parameter adjustment ensures sufficient lithium nitrate dissolution for quality film formation while maintaining overall electrolyte composition stability and preventing excessive ether content that could compromise stability
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 battery exhibits reduced internal resistance, increased capacity, and improved fast charging characteristics, maintaining performance even under high current density and in low-temperature conditions.
Implementation Method 1
a low-resistance film derived from lithium nitrate included in the electrolyte may be formed on the electrode surface during the charging and discharging process
Implementation Method 2
a lithium nitrate dissolution ratio, defined by Equation 1 below, in the electrolyte is 0.01 to 0.07
Data Source
AI summary
A lithium secondary battery according to the present disclosure includes: a cathode which includes a cathode active material layer including a lithium transition metal oxide; an anode disposed opposite to the cathode and including an anode active material layer, and an electrolyte which includes a lithium salt, a solvent including a carbonate solvent and an ether solvent, and lithium nitrate (LiNO3). In the electrolyte, a lithium nitrate dissolution ratio, defined by Equation 1, in the electrolyte is 0.01 to 0.07.