SiOx Electrode with Organic Surface Bonding for Battery Cycle Life
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Solution Overview
Problem
Nonaqueous electrolyte secondary cells face challenges in cycle characteristics due to large volume changes in silicon-based anode materials, leading to conductive path disconnection, active material separation, and peeling issues, which existing solutions like surface treatments and binders have not fully addressed.
Innovation Solution
An electrode with a collector and an active material layer containing SiOx particles (x ≤ 1.5) bonded with organic materials having phenylamino, imidazole, or amino groups, and a binder composed of sodium polyacrylate and optionally a water-soluble polymer, enhancing binding properties between the silicon-based active material, graphite, and conductive assistants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based active material is used to increase capacity, then the capacity increases significantly, but the volume change during charging and discharging becomes large causing pulverization and peeling
Solution Approach 1:
The invention changes the chemical composition parameter of the active material from pure silicon to silicon oxide (SiOx where x is 0.5-1.5), which fundamentally alters the volume expansion behavior during lithium ion insertion/extraction. This parameter change reduces the volume change from approximately 4 times for pure silicon to a more manageable level for SiOx, thereby suppressing pulverization and maintaining structural integrity over multiple cycles while retaining high capacity
Solution Approach 2:
The invention creates a composite material system consisting of silicon oxide particles combined with specific binders (polyacrylic acid or carboxymethyl cellulose) and conductive assistants. This composite approach leverages the high capacity of silicon oxide while the binder components provide mechanical support and adhesion, preventing peeling between the active material layer and current collector during volume changes
2Strength
If surface treatment with silane coupling agent is applied to prevent pulverization, then binding strength improves, but the type of binder is not specified leading to insufficient cycle characteristic improvement
Solution Approach 1:
The invention specifies precise chemical parameters for the binder components, using polyacrylic acid or carboxymethyl cellulose with defined functional groups (carboxyl groups). This parameter specification ensures optimal chemical interaction with the silicon oxide surface and conductive assistants, providing consistent adhesion strength that maintains electrode integrity throughout cycling operations
Solution Approach 2:
The binder acts as an intermediary material that chemically or physically connects the silicon oxide active material particles with the conductive assistant and current collector. The specific choice of polyacrylic acid or carboxymethyl cellulose provides favorable surface chemistry for bonding to both the inorganic silicon oxide and carbon-based conductive materials, ensuring strong interfacial adhesion that prevents peeling during volume expansion and contraction
3Strength
If heat treatment is applied to establish covalent binding between binder and active material, then binding strength increases, but the binding cannot be recovered during volume change leading to deteriorated cycle characteristics
Solution Approach 1:
The invention employs binders with dynamic bonding characteristics that can adapt to volume changes. The carboxyl-containing polymers form reversible or flexible bonds with the active material and conductive assistant, allowing the electrode structure to expand and contract during charging/discharging without permanent damage. This dynamic binding maintains electrical contact and mechanical integrity throughout cycling, unlike rigid covalent bonds that would fracture under repeated stress
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 proposed electrode configuration significantly improves binding strength and cycle characteristics of nonaqueous electrolyte secondary cells by maintaining strong interactions between the silicon-based active material, binder, and graphite, even during repeated charging and discharging cycles.
Implementation Method 1
SiOx particles (x ≤ 1.5) whose surfaces are bonded with an organic material having one or more functional groups selected from a group consisting of a phenylamino group, an imidazole group and an amino group
Implementation Method 2
the binder is composed of sodium polyacrylate and optionally a water-soluble polymer made of acrylic acid... enhancing binding properties between the silicon-based active material, graphite, and conductive assistants
Data Source
Figure 1~2
AI summary
Provided is an electrode for a nonaqueous electrolyte secondary cell capable of improving the cycle characteristics. An electrode (1) for a nonaqueous electrolyte secondary cell includes a collector (21) and an active material layer (10) formed on a surface of the collector (21) and containing an active material (11), a binder (14), and a graphite material (12). The active material (11) comprises SiOx particles whose surfaces are bonded with an organic material (11a) having one or more functional groups selected from the group consisting of a phenylamino group, an imidazole group and an amino group. The binder (14) is composed of a water-soluble polymer made of acrylic acid or a salt of the acrylic acid.