Mixed Cathode Material for Lithium Battery Thermal Safety
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Solution Overview
Problem
Current cathode active materials for lithium secondary batteries face challenges such as low thermal safety, high cost, and reduced capacity and output characteristics, particularly due to issues with lithium-containing cobalt oxides, manganese oxides, and nickel-based oxides, which suffer from phase transitions, instability, and chemical reactivity.
Innovation Solution
A cathode active material comprising a mixture of an overlithiated transition metal oxide and a lithium composite transition metal oxide, specifically formulated to enhance structural stability, capacity, and output characteristics, with optimized molar fractions and substitution of metals and anions to improve thermal safety and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium-containing cobalt oxides (LiCoO2) are used as cathode active material, then excellent lifespan characteristics and charge-discharge efficiencies are achieved, but thermal safety is low and cost is high
Solution Approach 1:
The patent uses a composite cathode active material consisting of Li1.2Ni0.1Mn0.6O2 (overlithiated transition metal oxide) and LiNi0.8Co0.1Mn0.1O2 (lithium composite transition metal oxide) in a weight ratio of 9:1 to 1:1. This composite structure combines the high capacity of nickel-rich materials with the structural stability of overlithiated materials, achieving both excellent lifespan characteristics and improved thermal safety.
2Object-affected harmful factors
If lithium manganese oxides (LiMnO2, LiMn2O4) are used as cathode active material, then high thermal safety and low cost are achieved, but capacity is low and high-temperature characteristics are poor
Solution Approach 1:
The patent changes the stoichiometric parameters by using overlithiated transition metal oxide (Li1.2Ni0.1Mn0.6O2) where the lithium content exceeds the stoichiometric ratio. This parameter change increases the capacity while maintaining thermal safety through the composite structure with lithium composite transition metal oxide.
3Quantity of substance
If lithium nickel-based oxides (LiNiO2) are used as cathode active material, then low cost and high discharge capacity are achieved, but crystal structure undergoes rapid phase transition and stability is reduced
Solution Approach 1:
The patent creates a composite material where Li1.2Ni0.1Mn0.6O2 (providing structural stability through overlithiation) and LiNi0.8Co0.1Mn0.1O2 (providing high discharge capacity) are combined. This composite structure prevents rapid phase transitions while maintaining high capacity and low cost.
4Duration of action of moving object
If nickel-based lithium transition metal oxides with metal substitution are used as cathode active material, then relatively excellent cycle characteristics are achieved, but swelling due to gas generation and reduced thermal safety occur over time
Solution Approach 1:
The patent optimizes the compositional parameters by precisely controlling the ratios of nickel, cobalt, and manganese in the lithium composite transition metal oxide (LiNi0.8Co0.1Mn0.1O2) and the overlithiation degree in Li1.2Ni0.1Mn0.6O2. This parameter optimization maintains cycle characteristics while preventing gas generation and swelling, thereby preserving thermal safety over time.
Data Source
AI summary
Disclosed are a cathode active material for lithium secondary batteries and a lithium secondary battery including the same and, more particularly, the present invention relates to a cathode active material for lithium secondary batteries that includes a mixture of an overlithiated transition metal oxide represented by Formula 1 below and a lithium composite transition metal oxide represented by Formula 2 below:Li1+aNibMncCo1-(a+b+c+d)MdO2-sAs (1)LiNixMnyCo1-(x+y+z)M′zO2-tA′t (2)wherein 0.1≦a≦0.2, 0.1≦b≦0.4, 0.3≦c≦0.7, 0≦d≦0.1, 0.5≦x≦0.8, 0.1≦y≦0.4, 0≦z≦0.1, 0≦s<0.2, and 0≦t<0.2;M and M′ are each independently at least one divalent or trivalent metal; andA and A′ are each independently at least one monovalent or divalent anion.