Li-Ion Battery Positive Electrode Resistivity Control
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Solution Overview
Problem
Lithium ion secondary batteries face performance deterioration and shortened cycle life due to changes in electrode resistivity during charging and discharging, as the binder in the active material layer swells, leading to increased resistance and compromised charging performance.
Innovation Solution
A lithium ion secondary battery design with a positive electrode having a volume resistivity between 100 Ωcm and 700 Ωcm after at least one charging and discharging cycle, achieved by forming active material layers on current collectors with specific compositions and structures, including lithium transition metal oxides and mixed carbon materials, to maintain high charging performance and extended cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric resistivity of the positive electrode is adjusted to be within the range of 10 Ω·cm to 450 Ω·cm, then the short-circuiting current can be suppressed and the deterioration in battery performance can be avoided, but the charging performance deteriorates and the cycle life is shortened due to binder swelling and resistance increase after charging and discharging cycles
Solution Approach 1:
The invention changes the parameter of volume resistivity from a static manufacturing parameter to a dynamic parameter monitored after charging and discharging cycles. By specifying the resistivity range (100-700 Ωcm) after at least one cycle, the invention accounts for binder swelling effects that occur during operation, thereby maintaining both short-circuiting suppression and acceptable cycle life.
Solution Approach 2:
The invention performs preliminary assessment of the positive electrode's volume resistivity after charging and discharging cycles before determining battery performance. This preliminary action allows prediction of cycle life and charging performance deterioration, enabling selection of electrodes that will maintain reliability throughout the battery's operational life.
2Reliability
If the electric resistivity of the positive electrode is adjusted to be within the range of 10 Ω·cm to 450 Ω·cm, then the short-circuiting current can be suppressed, but the charging performance deteriorates due to increased resistance after binder swelling
Solution Approach 1:
The invention changes the measurement timing of the resistivity parameter from pre-assembly to post-charging and discharging cycles. This parameter change reflects the actual operating conditions where binder swelling occurs, allowing optimization of charging performance while maintaining short-circuiting suppression.
Solution Approach 2:
The invention uses the volume resistivity measurement after charging and discharging cycles as feedback to evaluate and predict future charging performance. This feedback mechanism allows identification of electrodes that will maintain good charging performance throughout the battery's operational life.
3Duration of action of moving object
If the binder in the active material layer swells during charging and discharging, then the active material layer expands, but this causes increased resistance and performance deterioration
Solution Approach 1:
The invention monitors the change in volume resistivity as a parameter that reflects binder swelling and active material layer expansion during charging and discharging cycles. By specifying the resistivity range after at least one cycle, the invention accounts for these physical changes and their impact on electrode reliability.
Solution Approach 2:
The invention uses volume resistivity measurement as a simple, quick diagnostic tool to predict long-term electrode performance. This inexpensive parameter measurement allows identification of electrodes that will maintain low resistance throughout their operational life without requiring complex long-term testing.
Data Source
AI summary
Provided is a lithium ion secondary battery including a power generation element, the power generation element including a positive electrode, a negative electrode, a separator, and an electrolyte solution, the positive electrode including a positive electrode current collector, and a positive electrode active material layer provided for the positive electrode current collector, the positive electrode active material layer including a positive electrode active material and binder, the negative electrode including a negative electrode current collector and a negative electrode active material layer provided for the negative electrode current collector, the negative electrode active material layer including a negative electrode active material and binder. The positive electrode has a volume resistivity in a range of 100 Ωcm or more and 700 Ωcm or less after at least one charging and discharging cycle.