Lithium Ion Battery Pre-Charging Method for SEI Stability
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Solution Overview
Problem
Lithium ion secondary batteries with aprotic electrolyte solutions containing sulfonate esters and graphite negative electrodes often experience lithium compound deposition during initial charge, leading to decreased charge/discharge cycle characteristics over time.
Innovation Solution
A manufacturing method involving pre-charging the battery with a current between 0.05 C and 0.25 C and a voltage between 3.3 V and 3.5 V, using a cyclic or chain sulfonate ester, and a laminated structure to prevent lithium compound deposition on the negative electrode, ensuring high capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a lithium ion secondary battery uses an aprotic electrolyte solution containing a sulfonate ester having at least two sulfonyl groups and graphite as a negative electrode active material, then the battery achieves high initial reversible capacity and high electrode density, but lithium compound deposits on the negative electrode during initial charge, causing decreased charge/discharge cycle characteristics
Solution Approach 1:
The patent applies preliminary action by conducting a pre-charge process at a controlled current density (0.05 to 0.25 C) and voltage range (3.3 to 3.5 V) before regular charging. This preliminary charge forms a stable solid electrolyte interface (SEI) layer on the graphite negative electrode, preventing lithium compound deposition during subsequent charging cycles and thereby improving charge/discharge cycle characteristics while maintaining high initial reversible capacity
2Productivity
If the battery is charged at higher current to improve productivity, then the manufacturing efficiency increases, but lithium compound deposition occurs more readily, reducing battery reliability
Solution Approach 1:
The patent implements a two-stage charging process where the first stage (pre-charge) uses controlled current density (0.05 to 0.25 C) to form protective SEI layer, and the second stage (regular charge) can use higher current for improved productivity. This preliminary protective action enables subsequent faster charging without causing lithium compound deposition, thus resolving the contradiction between productivity and reliability
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 method effectively prevents lithium compound deposition and maintains high capacity retention rates over long periods, enhancing the battery's charge/discharge cycle characteristics.
Implementation Method 1
an aprotic electrolyte solution containing a sulfonate ester having at least two sulfonyl groups
Implementation Method 2
pre-charging the lithium ion secondary battery before pre-charge to fabricate a lithium ion secondary battery after pre-charge; the current for the pre-charge is 0.05 C or larger and 0.25 C or smaller, and the voltage thereof is 3.3 V or higher and 3.5 V or lower
Data Source
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AI summary
There is provided a lithium ion secondary battery exhibiting a high capacity retention rate over a long period. There is also provided a method for manufacturing a lithium ion secondary battery including a positive electrode, a negative electrode containing a negative electrode active material layer containing a graphite, an aprotic electrolyte solution containing a sulfonate ester having at least two sulfonyl groups, and a packaging material including a laminate film involving the positive electrode, the negative electrode and the aprotic electrolyte solution, the method including: enclosing the positive electrode, the negative electrode and the aprotic electrolyte solution in the packaging material to fabricate a lithium ion secondary battery before pre-charge; pre-charging the lithium ion secondary battery before pre-charge to fabricate a lithium ion secondary battery after pre-charge; and opening the enclosure of the packaging material of the lithium ion secondary battery after pre-charge, thereafter vacuum sealing the packaging material, and regularly charging the lithium ion secondary battery after pre-charge, wherein the current for the pre-charge is 0.05 to 0.25 C, and the voltage thereof is 3.3 to 3.5 V.