Over-Lithiated Cathode Composition for High-Voltage Cycle Reliability
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Solution Overview
Problem
Lithium secondary batteries using over-lithiated oxide particles exhibit inferior operational reliability and lifespan characteristics due to unique electrochemical reactions, particularly at high voltages, leading to deterioration in performance.
Innovation Solution
A cathode for lithium secondary batteries is designed with over-lithiated oxide particles having a specific composition and morphology, controlled electrochemically active surface area, and optimized XRD peak intensity ratio, along with a binder and conductive material, to enhance capacity and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If over-lithiated oxide particles are used as cathode active material, then capacity is improved (reversible capacity of 250 mAh/g or more), but operational reliability deteriorates (reduced lifespan characteristics)
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition parameters of over-lithiated oxide particles, specifically setting the stoichiometric ratios of lithium to transition metals (a/b≥1.05) and controlling the crystal structure parameters (combining C2/m and R3m space groups). This optimization allows achieving high capacity (250 mAh/g or more) while improving operational reliability by stabilizing the electrochemical reactions through proper parameter selection.
2Quantity of substance
If over-lithiated oxide particles with high lithium content are used, then reversible capacity increases (up to 250 mAh/g or more), but lifespan characteristics are reduced
Solution Approach 1:
The patent employs composite materials by creating over-lithiated oxide particles that contain multiple crystal structure domains (C2/m space group domains and R3m space group domains) within a single particle. This composite structure allows the material to benefit from the high capacity of over-lithiated oxide while the specific domain distribution stabilizes the particle structure during cycling, thereby extending lifespan characteristics.
3Quantity of substance
If lithium is inserted into transition metal sites to form over-lithiated oxide, then capacity is enhanced, but electrochemical stability at high voltages deteriorates
Solution Approach 1:
The patent applies local quality by creating distinct domains with different crystal structures (C2/m and R3m space groups) within the over-lithiated oxide particles. Each domain has localized structural characteristics that contribute to overall stability - the C2/m domains provide high capacity while the R3m domains offer structural stability at high voltages, thus resolving the contradiction between capacity enhancement and electrochemical stability.
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 cathode achieves improved capacity and lifespan characteristics by stabilizing the electrochemical reactions, preventing deterioration, and maintaining performance even at high voltages.
Implementation Method 1
A lithium secondary battery has a high operating voltage and a high energy density per unit weight... The lithium secondary battery may store an electric energy by a difference in chemical potential when lithium ions are intercalated and deintercalated between a cathode and an anode
Implementation Method 2
The over-lithiated oxide particles may exhibit a reversible capacity of 250 mAh/g or more by an electrochemical reaction of Li2MnO3... Li2MnO3 is electrochemically inactive, but may be converted into LiMnO2 as shown in Scheme 1 below by an activation process
Data Source
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AI summary
A cathode for a lithium secondary battery according to exemplary embodiments may include a cathode current collector; and a cathode active material layer formed on the cathode current collector and including over-lithiated oxide particles. An electrochemically active surface area of the cathode may be 0.5 m2/g to 2.5 m2/g.