Electrode binder mass ratio for lithium-ion battery cycle stability
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Solution Overview
Problem
The continuous production of a Solid Electrolyte Interface (SEI) layer during cyclic charge/discharge operations in Li-ion secondary batteries using sodium alginate as a binder leads to poor cycling performance, despite improved cycle characteristics.
Innovation Solution
An electrode for non-aqueous electrolyte secondary batteries is designed with an active material layer containing a conduction aid of acetylene black and vapor grown carbon fiber, where the mass ratios of acetylene black and vapor grown carbon fiber are within specific ranges, and a binder selected from salts of CMC, polyacrylic acid, or alginate, ensuring a mass ratio of 18% or more for the binder, which enhances cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sodium alginate is used as a binder in the electrode, then cycle characteristics are improved, but continuous SEI production occurs causing poor cycling performance
Solution Approach 1:
The patent changes the binder content parameter from conventional low levels (typically 5-10 mass%) to a high level of 18 mass% or more. This parameter change transforms the binder's function from merely holding active material particles together to actively suppressing continuous SEI production by forming a protective coating layer on the active material surface, thereby resolving the contradiction between improving cycle characteristics and preventing harmful substance loss.
2Reliability
If binder content is increased to suppress SEI production, then cycle characteristics improve, but electrode structure complexity increases
Solution Approach 1:
The patent applies parameter change by increasing the binder content to 18 mass% or more, which fundamentally alters the electrode's functional behavior. At this high concentration, the binder forms a continuous protective coating that simultaneously improves cycle characteristics and simplifies the overall electrode structure by eliminating the need for additional protective layers or complex formulations.
3Stability of the object's composition
If specific mass ratios of conduction aids are used, then conduction path stability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies precise mass ratio ranges for conduction aids (acetylene black: 12-20 mass%, vapor grown carbon fiber: 2-6 mass%) to optimize conduction path stability. These parameter specifications provide clear manufacturing targets that balance the need for stable electrical conduction with practical manufacturability, ensuring reliable performance while maintaining reasonable production feasibility.
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 electrode achieves improved cycle characteristics and high capacity maintenance by minimizing conduction path cutoff and maintaining a mechanically stable coating layer, thereby enhancing the overall performance of non-aqueous electrolyte secondary batteries.
Implementation Method 1
the coating layer is reinforced by VGCF so as to obtain a mechanically-stable coating layer
Implementation Method 2
the surface of the active material is covered with resin (binder 2)
Implementation Method 3
The conduction aid contains acetylene black and a vapor grown carbon fiber
Data Source
Figure 1
AI summary
An electrode for a non-aqueous electrolyte secondary battery is provided in which cycle characteristics are improved and a charging/discharging capacity is secured. The electrode of a non-aqueous electrolyte secondary battery according to the present embodiment is provided with an active material layer containing a conduction aid, an active material (1) that contains SiOx and a binder (2) of alginic acid. The conduction aid contains acetylene black and a vapor grown carbon fiber (3). A mass ratio of the acetylene black is within a range of from 12 mass% to 20 mass% inclusive with respect to a mass of the active material, a mass ratio of the vapor grown carbon fiber is within a range of from 2 mass% to 6 mass% inclusive with respect to a mass of the active material, and a mass ratio of the binder is within a range of from 18 mass% to 21 mass% inclusive with respect to a mass of the active material (1).