Nonaqueous Battery Electrolyte with Nitrile Compound
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Solution Overview
Problem
Nonaqueous secondary batteries with lithium composite oxides as positive electrode active materials face issues with increased film resistance at the electrode-electrolyte interface, leading to inhibited ion conduction, decreased capacity efficiency, and poor charge load characteristics when stored at high temperatures or charged in low-temperature environments.
Innovation Solution
Incorporating a nitrile group-containing compound in the nonaqueous electrolyte and a silane or aluminum coupling agent in the positive electrode binder, with specific concentrations and particle size ranges for the active material, to form a protective film that suppresses oxidative decomposition and enhances electrochemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a nonaqueous electrolyte is used with a lithium composite oxide positive electrode, then high energy density and high capacity are achieved, but film resistance increases at the electrode-electrolyte interface leading to inhibited ion conduction
Solution Approach 1:
A silane coupling agent is introduced as an intermediary substance between the lithium composite oxide positive electrode and the nonaqueous electrolyte. The coupling agent forms a protective film on the electrode surface that mediates the interface, reducing film resistance while maintaining the high energy density benefits of the lithium composite oxide system.
Solution Approach 2:
The invention changes the chemical composition parameters of the electrolyte by adding specific compounds (cyclic carbonate and chain carbonate in controlled ratios). This parameter change optimizes the interface properties, reducing film resistance without sacrificing the high capacity and energy density characteristics.
2Quantity of substance
If the battery is stored at high temperature in a charged state, then the positive electrode is readily degraded through oxidative decomposition, but maintaining high capacity requires stable electrode structure
Solution Approach 1:
The silane coupling agent is applied in advance to the positive electrode surface before battery assembly and storage. This preliminary action creates a protective film that prevents oxidative decomposition during high-temperature storage, preserving both the electrode structure and capacity.
Solution Approach 2:
The coupling agent acts as a protective intermediary layer between the positive electrode and the electrolyte, preventing direct contact and oxidative decomposition reactions during high-temperature storage, thus maintaining both structural stability and capacity.
3Object-generated harmful factors
If a protective film is formed on the positive electrode to suppress oxidative decomposition, then gas generation is reduced at high temperature, but charge load characteristics deteriorate in low temperature environments
Solution Approach 1:
The invention optimizes the composition parameters of the electrolyte (cyclic carbonate 10-40 vol%, chain carbonate 60-90 vol%) and the coupling agent concentration to create a protective film with balanced properties. This parameter optimization ensures the film suppresses gas generation at high temperature while maintaining adequate ion conductivity for charge load characteristics at low temperature.
Solution Approach 2:
The protective film formed by the coupling agent provides localized protection at the electrode surface where oxidative decomposition occurs, while the bulk electrolyte composition is optimized to maintain ion conductivity. This local quality approach allows gas suppression at the interface without compromising overall charge load 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 effectively reduces gas generation at high temperatures, maintains capacity efficiency, and improves charge load characteristics in low-temperature environments by optimizing the interface resistance and electrochemical reactions.
Implementation Method 1
the nitrile group-containing compound is adsorbed on a positive electrode in a charged state, it is considered that the compound has advantageous effects of protecting the surface of the positive electrode
Implementation Method 2
the nitrile group-containing compound is adsorbed on a positive electrode in a charged state
Implementation Method 3
a silane coupling agent having an organic reactive group such as an epoxy group and amino group and a bonding group such as a methoxy group and ethoxy group is dispersed in a positive electrode binder in order to improve wettability of a positive electrode with an electrolyte
Implementation Method 4
lithium transition-metal composite oxides represented by LiMO2 (where M is at least one of Co, Ni, and Mn), (namely, LiCoO2, LiNiO2, LiNiyCo1-yO2 (y=0.01 to 0.99), LiMnO2, LiMn2O4, LiCoxMnymNizO2 (x+y+z=1)), LiFePO4, and the like, all of which can reversibly absorb and desorb lithium ions
Data Source
AI summary
A nonaqueous electrolyte of nonaqueous secondary battery contains a nitrile group-containing compound at a concentration of 0.05% by mass or more. A positive electrode active material has an average particle diameter of 4.5 to 15.5 μm and a specific surface area of 0.13 to 0.80 m2/g. A positive electrode binder layer contains a silane coupling agent and/or at least one of aluminum, titanium, or zirconium based coupling agent having an alkyl or an alkoxy groups having 1 to 18 carbon atoms at a content of 0.003% by mass or more and 5% by mass or less. Thus nonaqueous secondary battery having a film resistance of the interface between a positive electrode and the electrolyte being less increased, and excellent ion conductivity and charge load characteristics in a low temperature environment is provided.