Ti-Oxide Negative Electrode Binder Ratio Against Electrolyte Depletion
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Solution Overview
Problem
Aqueous lithium secondary batteries face issues with volume changes in titanium composite oxides during charge and discharge, leading to electrolyte depletion and electrolysis, which degrades charge-and-discharge characteristics, and reducing electrode density to prevent depletion can cause water electrolysis.
Innovation Solution
A battery design with a negative electrode active material-containing layer incorporating a Ti-containing oxide and a binder capable of containing water, where the binder content is between 0.2% and 15% by weight relative to the water content in the electrolyte, using a soluble binder like polyvinylidene fluoride to prevent dissolution and enhance adhesion, thereby suppressing hydrogen gas generation and maintaining electrolyte retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrode density is reduced to prevent electrolyte depletion, then electrolyte depletion is prevented, but water electrolysis occurs easily resulting in degradation of charge-and-discharge characteristics
Solution Approach 1:
The invention changes the chemical composition parameters of the binder by specifying it contains carboxymethyl cellulose and/or styrene-butadiene rubber in specific proportions (0.1-10 wt% of active material), which alters the electrode's interaction with electrolyte to prevent both depletion and electrolysis
Solution Approach 2:
The invention uses a composite binder system combining carboxymethyl cellulose and styrene-butadiene rubber in specific ratios, creating a material that simultaneously provides structural stability to prevent electrolyte depletion while suppressing water electrolysis through the synergistic effects of the composite components
2Productivity
If titanium composite oxide volume change is accommodated, then charge-and-discharge capacity is maintained, but electrolyte depletion and breakage of electron-conducting path occur
Solution Approach 1:
The invention uses a flexible polymer binder system that can accommodate the volume expansion and contraction of titanium composite oxide during charge-discharge cycles, maintaining continuous electron conduction paths despite the mechanical stress from volume changes
Solution Approach 2:
The invention optimizes the binder composition parameters (specifically incorporating carboxymethyl cellulose and styrene-butadiene rubber in defined proportions) to create a matrix that flexibly adapts to volume changes while preventing electrolyte depletion and maintaining electron conductivity
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 improves the charge-and-discharge cycle performance by preventing electrolyte depletion and electrolysis, ensuring better adhesion between the active material layer and current collector, and maintaining electrolyte retention within the battery.
Implementation Method 1
a binder capable of containing water
Implementation Method 2
excessively reducing the electrode density in aqueous batteries such as aqueous lithium secondary batteries can easily cause electrolysis of water
Data Source
AI summary
In general, according to one embodiment, a battery including a positive electrode, a negative electrode, and a water-containing electrolyte is provided. The negative electrode includes a negative electrode active material-containing layer that includes a Ti-containing oxide and a binder capable of containing water. Also, the battery satisfies the following expression (1):0.2≤Wbind/WH2O≤15(1)where Wbind denotes a content (% by weight) of the binder capable of containing water in the negative electrode active material-containing layer, and WH2O denotes a content (% by weight) of the water in the electrolyte.