Layered Lithium-Composite Cathode for Low Voltage Fade
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Solution Overview
Problem
Current lithium ion secondary batteries face challenges in achieving high energy density, low voltage drop during repeated charge/discharge, and excellent cycle and rate properties, particularly for applications like electric cars, where batteries with high capacity and light weight are demanded.
Innovation Solution
A positive electrode active material comprising a layered lithium-composite oxide with specific compositions of Li, Ni, Mn, and optionally Co, optimized through a method involving the synthesis of a carbonate precursor compound and calcination under controlled conditions to achieve a peak intensity ratio and energy density within specified ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If LiNiO2 is used as positive electrode active material to achieve large charge/discharge capacity, then energy density is improved, but heat stability and cycle property deteriorate
Solution Approach 1:
The patent uses a composite oxide material containing Li, Ni, Co, and Mn in specific ratios (Li:Ni:Co:Mn = 1.05:0.30:0.05:0.65) to combine the high capacity benefits of LiNiO2 with the stability benefits of LiCoO2 and LiMnO3, achieving both high energy density and good cycle property
Solution Approach 2:
The patent optimizes the compositional parameters of the composite oxide, specifically adjusting the ratios of Li, Ni, Co, and Mn elements, as well as controlling the average particle size (10-20 μm) and surface area (5-15 m²/g) to achieve optimal performance balance
2Use of energy by moving object
If Li2MnO3-containing positive electrode active material is used to increase capacity, then discharge capacity is improved, but voltage drop during repeated charge/discharge increases
Solution Approach 1:
The patent creates a composite oxide where Li2MnO3 is combined with LiCoO2 and LiNiO2 phases, where the LiCoO2 component provides structural stability and voltage stability during cycling, while the Li2MnO3 component contributes to high discharge capacity
Solution Approach 2:
The patent creates different phases within the composite material that perform different functions: LiCoO2-rich regions provide voltage stability, LiMnO3-rich regions provide high capacity, and the overall composite achieves both properties simultaneously
3Use of energy by moving object
If existing composite oxide or lithium-metal oxide materials are used, then discharge capacity is improved, but energy density and cycle property cannot fully satisfy demands
Solution Approach 1:
The patent precisely controls multiple parameters including the molar ratios of Li:Ni:Co:Mn (1.05:0.30:0.05:0.65), average particle size (10-20 μm), and specific surface area (5-15 m²/g) to optimize both energy density retention and discharge capacity simultaneously
Data Source
AI summary
When a non-aqueous electrolyte secondary battery in which a positive electrode active material comprising a layered lithium-composite oxide is used for a positive electrode is subjected to charge/discharge under a prescribed condition, in a graph showing the relationship between voltage “V” with discharge during 5th cycle and value dQ/dV from differentiation of battery capacity “Q” with discharge during 5th cycle by voltage “V”, peak intensity ratio “r” represented by the equation: r=|Ic|/(|Ia|+|Ib|+|Ic|) satisfies 0<r≤0.25, in which |Ia| is absolute value dQ/dV for a peak top within a range of more than 3.9V to 4.4V or less, |Ib| is absolute value dQ/dV for a peak top within a range of more than 3.5V to 3.9V or less, and |Ic| is absolute value dQ/dV for a peak top within a range of 2.0V or more to 3.5V or less.