Non-Aqueous Secondary Battery Formation to Suppress Black Regions
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries with larger electrode active material layers exhibit charging unevenness due to gas production during initial charging, leading to the formation of black regions with higher resistance, which degrade battery performance.
Innovation Solution
A production method involving initial charging followed by a controlled temperature maintenance at 50° C or lower for at least 72 hours, with the battery assembly restrained to facilitate gas release, ensuring a good-quality SEI coating formation and suppressing the formation of black regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the formation width of electrode active material layer is enlarged to satisfy higher energy demands, then battery energy capacity is improved, but charging unevenness occurs due to gas production during initial charging
Solution Approach 1:
The patent applies preliminary action by performing initial charging at a reduced rate (0.1C or lower) before normal charging. This preliminary charging step allows gas to be gradually released during initial charging, preventing gas accumulation that would cause charging unevenness in large-format batteries, thereby enabling the use of larger electrode active material layers without compromising charging uniformity.
2Reliability
If initial charging is performed to form SEI coating on negative electrode plate, then battery performance is improved, but gas production occurs in electrode body causing charging unevenness
Solution Approach 1:
The patent converts the harmful effect of gas production into a beneficial process by designing the initial charging to occur at reduced rates, allowing gas to be gradually released and utilized to form a more uniform SEI coating. The gas evolution during controlled initial charging helps create a more homogeneous electrolyte distribution and SEI layer, transforming what is typically a harmful byproduct into a beneficial mechanism for improving battery performance.
3Manufacturing precision
If black regions are formed in wound electrode body due to gas production during initial charging, then local resistance increases, but battery characteristics such as capacity retention rate deteriorate
Solution Approach 1:
The patent applies preliminary action by performing a first charging step at reduced rates (0.1C or lower) before normal charging operations. This preliminary charging prevents gas accumulation that would lead to black region formation and coating non-uniformity, thereby maintaining low local resistance and preserving capacity retention rate throughout the battery lifecycle.
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 method effectively reduces the formation of black regions, maintaining battery performance by ensuring uniform resistance and capacity retention in non-aqueous electrolyte secondary batteries.
Implementation Method 1
The initial charging can form a so-called SEI coating on the surface of a negative electrode plate
Implementation Method 2
gas derived from components in a secondary battery assembly can be produced in the electrode body during initial charging
Data Source
AI summary
Provided is a technique for suppressing the formation of black regions in a wound electrode body. The production method disclosed herein is a method for producing a non-aqueous electrolyte secondary battery that includes a wound electrode body, a non-aqueous electrolyte, and a battery case. This production method includes the following steps: an assembling step S1 of placing the wound electrode body and the non-aqueous electrolyte in the battery case to construct a secondary battery assembly; a first step S2 of performing initial charging on the secondary battery assembly; and a second step S3 of setting the temperature of the wound electrode body to 50° C. or lower and keeping this state for at least 72 hours after the first step.