Hard Carbon Anode Charging for Overcharge-Safe Li-Ion Capacity
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Solution Overview
Problem
Lithium ion secondary batteries with hardly graphitizable carbonaceous materials face challenges in achieving high charge capacity and charge-discharge efficiency due to issues like lithium ion utilization efficiency and thermal stability, especially when overcharged, which can lead to safety concerns and reduced performance.
Innovation Solution
A method of charging nonaqueous electrolyte secondary batteries using a hardly graphitizable carbonaceous material with controlled oxygen content, derived from plant sources, and processed through acid treatment and calcination to optimize lithium storage and reduce impurities, ensuring high charge capacity and efficiency by maintaining lithium ions within the material until just before metallic lithium precipitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If constant-current constant-voltage charging method is used to ensure safety against overcharging, then reliability is improved, but charge-discharge efficiency deteriorates
Solution Approach 1:
The patent changes the charging parameter from conventional constant-current constant-voltage method to a method based on dV/dt (rate of voltage change). By monitoring the rate of voltage change during charging and adjusting the charging current accordingly, the system achieves both safety and high efficiency. Specifically, when dV/dt exceeds a predetermined threshold, the charging current is reduced or stopped, preventing overcharging while allowing faster charging rates than conventional methods.
2Quantity of substance
If hardly graphitizable carbonaceous material is used to increase charge capacity beyond 372 mAh/g, then charge capacity is improved, but lithium ion utilization efficiency and thermal stability deteriorate
Solution Approach 1:
The patent applies preliminary treatment to the hardly graphitizable carbonaceous material before battery assembly. This includes surface modification and controlled carbonization processes that prepare the material to accept and retain lithium ions more effectively. The preliminary action of surface treatment creates favorable conditions for subsequent lithium ion insertion, improving utilization efficiency and thermal stability while maintaining the high capacity advantage of the material.
Solution Approach 2:
The patent modifies the physical and chemical parameters of the hardly graphitizable carbonaceous material through controlled carbonization temperature, heating rate, and atmosphere composition. By optimizing these parameters, the material achieves a balance between high lithium ion capacity and improved thermal stability, resolving the contradiction between quantity 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 results in nonaqueous electrolyte secondary batteries with extremely high charge capacity and charge-discharge efficiency, reducing lithium ion utilization inefficiencies and enhancing safety by minimizing oxygen content and impurities, thus improving battery performance and stability.
Implementation Method 1
the hardly graphitizable carbonaceous material is capable of doping (charging) and dedoping (discharging) of lithium
Implementation Method 2
processed through acid treatment and calcination to optimize lithium storage and reduce impurities
Implementation Method 3
processed through acid treatment and calcination to optimize lithium storage and reduce impurities
Data Source
Figure 1~2
AI summary
To provide a hardly graphitizable carbonaceous material used in a negative electrode material for nonaqueous electrolyte secondary batteries (for example, a lithium ion battery) having not only high charge capacity but also high charge-discharge efficiency and being fully charged to be used and a method for producing the same. To provide a negative electrode material for nonaqueous electrolyte secondary batteries comprising such a hardly graphitizable carbonaceous material, and a nonaqueous electrolyte secondary battery comprising such a negative electrode material for nonaqueous electrolyte secondary batteries and being fully charged to be used. A hardly graphitizable carbonaceous material, being a hardly graphitizable carbonaceous material for nonaqueous electrolyte secondary batteries fully charged to be used and having an oxygen element content of 0.25% by mass or less.