Aqueous Secondary Battery Electrode Interface for Water-Splitting Suppression
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Solution Overview
Problem
Nonaqueous lithium secondary batteries face safety concerns due to flammability of organic solvents, high internal resistance, and instability in charge-discharge cycles, while aqueous solution batteries suffer from electrolysis issues leading to active material detachment and low energy density.
Innovation Solution
A secondary battery design incorporating a titanium-containing oxide negative electrode active material, a separation layer with specific metal concentrations of Hg, Pb, Zn, or Bi, and an aqueous electrolyte to suppress water splitting and hydrogen generation, enhancing charge-discharge efficiency and cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If an organic solvent electrolyte solution is used to achieve high electromotive force and oxidation resistance, then the battery can operate at 2V to 4.5V, but the safety deteriorates due to flammability of the organic solvent
Solution Approach 1:
The patent changes the fundamental parameter of the electrolyte from organic solvent to aqueous solution, fundamentally altering the chemical composition to eliminate flammability while managing the associated electrochemical challenges through material selection
Solution Approach 2:
The patent converts the harmful effect of water (electrolysis at low potentials) into a beneficial outcome by strategically selecting electrode materials with potentials that utilize water's electrochemical stability window, thereby achieving both safety and performance
2Reliability
If an aqueous solution electrolyte is used to improve safety, then the battery becomes non-flammable, but the active material falls off the current collector due to electrolysis of water
Solution Approach 1:
The patent changes the electrochemical potential parameters of the electrode materials to fall within the water stability window, preventing water electrolysis and the associated degradation issues while maintaining aqueous electrolyte safety benefits
Solution Approach 2:
The patent employs composite electrode material systems (lithium manganese oxide with lithium vanadium oxide or lithium titanium oxide) that work synergistically to achieve stable operation in aqueous electrolyte, combining the advantages of different materials to overcome individual limitations
3Stability of the object's composition
If lithium manganese oxide and lithium vanadium oxide are used as electrode materials to avoid water electrolysis, then charge-discharge stability improves, but the energy density becomes insufficient
Solution Approach 1:
The patent optimizes the electrochemical potential parameters and material composition ratios to maximize the energy density within the constraints of aqueous electrolyte stability, extracting maximum energy from the available potential window
4Quantity of substance
If a nonaqueous lithium secondary battery is used to achieve high energy density, then the battery performance improves, but the internal resistance increases due to inferior electrical conductivity of the electrolyte solution
Solution Approach 1:
The patent changes the electrolyte phase from nonaqueous to aqueous, fundamentally improving electrical conductivity and reducing internal resistance while managing the associated electrochemical challenges through careful material selection
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 suppresses water splitting and hydrogen production, leading to improved charge-discharge efficiency and extended cycle life, addressing safety and performance issues in both nonaqueous and aqueous lithium secondary batteries.
Implementation Method 1
it is considered that water splitting and hydrogen generation are suppressed by the first metal element having a high hydrogen generation overvoltage
Implementation Method 2
a nonaqueous lithium secondary battery using a carbon material or a lithium titanium oxide as a negative electrode active material and a layered oxide that contains nickel, cobalt or manganese as a positive electrode active material
Implementation Method 3
an aqueous electrolyte. At least one of the negative electrode active material-containing layer and the separation layer contains one or more first metal element
Data Source
AI summary
Provided is a secondary battery including a negative electrode, a positive electrode, a separation layer in contact with an active material-containing layer of the negative electrode, and an aqueous electrolyte. A first concentration corresponding to a first metal concentration represented by Equation 1 (first metal concentration=atomic concentration of Hg, Pb, Zn, and/or Bi/sum of atomic concentrations of elements B to U in periodic table, excluding carbon and oxygen) in a boundary region between the active material-containing layer and the separation layer is 2% or more and 8.2% or less. A ratio of the first concentration to a second concentration corresponding to the first metal concentration represented by Equation 1 in the active material-containing layer excluding the boundary region is 2.5 or more and less than 4.