LMR Cathode Pretreatment for Higher Initial Coulombic Efficiency
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Solution Overview
Problem
Lithium-manganese-rich (LMR) materials for rechargeable lithium batteries suffer from low coulombic efficiency in the initial formation cycle, leading to increased negative electrode usage and offsetting the cost advantage of the positive electrode, necessitating improved coulombic efficiency to optimize the negative to positive ratio (N/P) in full-cell design.
Innovation Solution
A pretreatment method involving charge/discharge processes with a higher charge current density than discharge current density is applied to activate the redox reactions of the LMR positive electrode active material, enhancing initial coulombic efficiency without increasing formation time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional formation process is used for LMR materials, then formation time is reduced, but initial coulombic efficiency remains low
Solution Approach 1:
The patent applies preliminary action by performing a pretreatment charge/discharge cycle before the conventional formation process. This preliminary step activates the LMR positive electrode material by inducing redox reactions, which improves initial coulombic efficiency without significantly increasing total formation time. The pretreatment prepares the material in advance for better performance during subsequent formation cycles.
2Ease of manufacture
If LMR materials are used to reduce cost, then positive electrode material cost decreases, but negative electrode usage increases due to low coulombic efficiency
Solution Approach 1:
The patent implements feedback by using the charge/discharge performance data from the pretreatment cycle to optimize the formation process parameters. By monitoring coulombic efficiency and adjusting subsequent formation conditions based on this feedback, the process maximizes the benefit of using low-cost LMR materials while minimizing the required negative electrode capacity, thereby reducing overall battery cost.
3Reliability
If charge current density is increased during pretreatment, then coulombic efficiency improves, but formation time may increase
Solution Approach 1:
The patent applies parameter changes by optimizing the charge current density during the pretreatment cycle. Specifically, it uses a charge current density of 0.1 C or higher (such as 0.2 C, 0.5 C, or 1.0 C) which is sufficiently high to activate redox reactions and improve coulombic efficiency, yet controlled to prevent excessive formation time. This parameter optimization balances efficiency improvement with time constraints.
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 improves discharge capacity and reversible discharge capacity ratio, reducing the formation time and maintaining battery production rates while increasing the coulombic efficiency to above 89%, thus optimizing the N/P ratio and energy density.
Implementation Method 1
In addition to oxidation-reduction of existing transition metals, LMR materials may be applied with a new principle of oxygen oxidation-reduction (O-redox) to exhibit high capacity
Data Source
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AI summary
A pretreatment method is provided for activating a lithium-manganese-rich positive electrode active material includes performing charge/discharge under a condition in which a charge current density (I1) is higher than a discharge current density (I2), and a positive electrode and a rechargeable lithium battery to which the pretreatment method is applied are provided.