Non-aqueous Battery Capacity Balance via Negative Electrode Additive
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries face challenges in achieving high capacity and long life, particularly when charged to high voltages, due to irreversible lithium ion loss and reactivity issues with nickel-containing lithium composite oxides, leading to reduced efficiency and potential gas generation.
Innovation Solution
A non-aqueous electrolyte secondary battery design incorporating a nickel-containing lithium composite oxide positive electrode, a graphite negative electrode with an additive that reacts at higher potentials, and a specific weight ratio and cut-off voltage range to balance capacities and prevent lithium deposition, along with a solid solution containing manganese and other elements to enhance thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the end of charge voltage is set higher than 4.2 V to improve capacity, then the battery capacity increases, but the irreversible capacity loss increases and lithium ions remain trapped in the negative electrode
Solution Approach 1:
An additive layer is applied to the negative electrode before the main graphite active material. This additive layer performs the preliminary function of consuming excess lithium ions through irreversible reaction, preventing them from being trapped in the graphite structure and causing capacity loss in subsequent cycles.
Solution Approach 2:
The additive layer acts as an intermediary between the positive electrode and the graphite negative electrode. It mediates the lithium ion transfer by selectively consuming excess lithium ions, allowing the graphite to function at its full theoretical capacity while maintaining charge-discharge balance.
2Quantity of substance
If an additive is added to the negative electrode to balance irreversible capacities, then the effective capacity improves, but the positive electrode potential increases accelerating gas generation
Solution Approach 1:
The invention changes the voltage parameter by setting the charge cut-off voltage to a specific range (4.25-4.6 V). This parameter optimization balances the electrochemical reactions, achieving effective capacity improvement while controlling the positive electrode potential to minimize gas generation from electrolyte decomposition.
3Quantity of substance
If nickel-containing lithium composite oxide is used to increase theoretical capacity, then the battery capacity increases, but the reactivity with non-aqueous electrolyte increases causing gas generation
Solution Approach 1:
The charge cut-off voltage is optimized to 4.25-4.6 V, which balances the reactivity of nickel-containing lithium composite oxide with the non-aqueous electrolyte. This parameter control prevents excessive gas generation while maintaining the high theoretical capacity benefits of the nickel-based material.
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 solution results in a battery with improved high-capacity and long-life characteristics by balancing the capacities of the electrodes and reducing reactivity, thereby enhancing cycle stability and preventing lithium deposition on the negative electrode.
Implementation Method 1
an additive that reacts with lithium at a potential higher than a maximum potential of graphite during charge and discharge
Data Source
AI summary
Disclosed is a non-aqueous electrolyte secondary battery comprising a positive electrode containing a nickel-containing lithium composite oxide, a negative electrode containing graphite, and a non-aqueous electrolyte. The cut-off voltage of charge of this non-aqueous electrolyte secondary battery is 4.25 to 4.6 V. The negative electrode contains an additive that reacts with lithium at a potential higher than the potential of graphite. The ratio A/B of a positive electrode capacity A based on the weight of the nickel-containing lithium composite oxide and the cut-off voltage of charge relative to a weight B of the graphite contained in a portion of a negative electrode material mixture layer opposing to a positive electrode material mixture layer is 300 to 340 mAh/g, and the irreversible capacity C of the positive electrode and the irreversible capacity D of the negative electrode in the portion opposing to the positive electrode satisfies C≧D.