Battery Charging Profile and Separator Adhesion for High-Voltage Cycling
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Solution Overview
Problem
Lithium-ion batteries face high temperature cycle failure due to prolonged high voltage charging and gas expansion, exacerbated by weak adhesion between electrodes and separators, leading to increased interface reactions and capacity retention issues.
Innovation Solution
Implementing a method that uses a high-adhesion separator with a bonding force greater than or equal to 3 N/m and a staged charging approach, where the battery is charged with a first-stage current until a first-stage voltage, then with a second-stage current at a higher voltage but lower current, to reduce cathode exposure time and interface reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the charge limiting voltage is increased to improve energy density, then the energy storage capacity is improved, but the cathode structure is damaged and side reactions occur
Solution Approach 1:
The separator is pre-treated to form a dense cross-linked gel layer on its surface before battery operation. This preliminary protective layer prevents direct contact between the cathode and electrolyte, reducing interface reactions and protecting the cathode structure even when charged at high voltages that would normally cause damage.
Solution Approach 2:
The cross-linked gel layer on the separator acts as an intermediary between the cathode and electrolyte. It mediates the interaction by providing a physical barrier that reduces direct contact, thereby suppressing side reactions while still allowing necessary ion transport, enabling high voltage charging without cathode degradation.
2Reliability
If electrolyte formulation is optimized to improve high temperature cycling life, then cycling performance is improved, but other battery performance parameters deteriorate
Solution Approach 1:
The cross-linked gel layer on the separator serves as an intermediary that protects the cathode from electrolyte contact. This reduces interface reactions and improves high temperature cycling life without requiring electrolyte formulation changes, thereby maintaining good low temperature discharge and high rate charging performance.
Solution Approach 2:
The separator undergoes parameter changes through cross-linking treatment, transforming from a conventional separator to one with a dense gel layer. This structural parameter change enables the separator to provide protective functions that improve cycling life without affecting other performance parameters.
3Stability of the object's composition
If the bonding force between separator and electrodes is increased to suppress bloating, then structural stability is improved, but manufacturing complexity increases
Solution Approach 1:
The separator is treated to form a cross-linked gel layer, changing its physical and chemical parameters. This cross-linked structure provides strong bonding to electrode surfaces, suppressing bloating and maintaining structural stability during high voltage charging cycles.
Solution Approach 2:
The separator becomes a composite structure with a base layer and a cross-linked gel layer on its surface. This composite structure combines the functions of the base separator with the protective and bonding properties of the cross-linked gel layer, achieving both structural stability and ease of manufacture.
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 significantly improves battery cycling performance by reducing side reactions and bloating, enhancing capacity retention and stability at high temperatures.
Implementation Method 1
a bonding force between the separator and the positive electrode, and/or a bonding force between the separator and the negative electrode are greater than or equal to 3 N/m
Data Source
AI summary
A method for improving cycling performance of a battery includes, in a first stage, charging the battery with a first-stage current until a voltage of the battery reaches a first-stage voltage value and in a second stage, charging the battery with a second-stage current until the voltage of the battery reaches a second-stage voltage value. The second-stage voltage value is greater than the first-stage voltage value, and the second-stage current is less than the first-stage current.