Gradient Binder Electrode Structure for Battery Safety
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Nonaqueous electrolyte secondary batteries, such as lithium ion batteries, face safety issues due to heat generation from overcharge or internal short circuits, which increase internal resistance and hinder power output, as existing solutions either increase internal resistance or fail to adequately prevent large current flows during short circuits.
Innovation Solution
A nonaqueous electrolyte secondary battery design featuring a positive or negative electrode with a material mixture layer comprising a first layer and a second layer, where the volume ratio of the binder to the active material differs, with a lower ratio in the first layer contacting the current collector and a higher ratio in the surface layer, increasing resistance between electrodes while maintaining normal battery characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the resistance of the active material is increased to suppress heat generation during short circuit, then safety is improved, but internal resistance increases and power output deteriorates
Solution Approach 1:
The electrode is divided into two distinct layers: a first layer in contact with the current collector and a second layer on the outer surface. Each layer has different binder volume ratios, creating a gradient structure where the inner layer maintains low resistance for power output while the outer layer provides high resistance for safety during short circuits
Solution Approach 2:
Different regions of the electrode are assigned different properties: the first layer (inner) has low binder content for conductivity and power, while the second layer (outer) has high binder content for resistance and safety. This local differentiation resolves the contradiction by optimizing each region for its specific function
2Reliability
If a resistance layer is formed on the current collector surface to prevent large current flow during short circuit, then safety is improved, but internal resistance increases and battery characteristics deteriorate
Solution Approach 1:
The resistance function is localized to the second layer only, while the first layer maintains low resistance for normal operation. This spatial differentiation of resistance properties allows safety without compromising overall battery characteristics
Solution Approach 2:
Instead of using a single uniform layer, the invention introduces a vertical dimension with two layers having different resistance properties. This layered approach allows simultaneous optimization of safety (outer layer) and performance (inner layer)
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
This design effectively prevents overheating during overcharge or internal short circuits by increasing resistance between electrodes, maintaining battery performance and safety without significantly increasing internal resistance, thus ensuring high safety and excellent battery characteristics.
Implementation Method 1
the volume ratio (A) of the binder in the first layer which is in contact with the surface of the current collector is lower than the volume ratio (B) of the binder in the second layer
Implementation Method 2
The nonaqueous electrolyte may be an aprotic organic solvent dissolving therein lithium salt such as LiClO4, LiPF6 or the like
Implementation Method 3
a nonaqueous electrolyte dissolving therein lithium salt such as LiClO4, LiPF6 or the like
Implementation Method 4
As the active material of the positive electrode, lithium composite oxides capable of reversibly causing an electrochemical reaction with lithium may be used
Implementation Method 5
Heat generated by the reaction accelerates the oxygen elimination from the positive electrode active material. This chain reaction is considered as a main cause of the heat generation of the battery
Data Source
AI summary
A nonaqueous electrolyte secondary battery comprising a positive electrode 5, a negative electrode 6, a separator 7 and a nonaqueous electrolyte, wherein a material mixture layer containing an active material and a binder is formed on a surface of a current collector 51 of at least one of the positive electrode 5 and the negative electrode 6. The material mixture layer includes a first layer 52 and a second layer 53 which are different in volume ratio of the binder to the active material. The volume ratio (A) of the binder in the first layer 52 in contact with the surface of the current collector 51 is lower than the volume ratio (B) of the binder in the second layer 53.