Composite Positive Electrode Material for Lithium-Ion Battery
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Solution Overview
Problem
Conventional lithium-ion secondary batteries face challenges in maintaining high capacity and initial charge/discharge efficiency due to unstable crystal structures and insufficient discharge capacity and operation voltage in lithium-nickel-manganese composite oxides and cathode compositions.
Innovation Solution
A positive electrode active material comprising a transition metal oxide with a specific layered-spinel composite structure, including a first active material with a formula Li1.5[Ni a Co b Mn c [Li]d]O3 and a second active material with a spinel-type structure, optimized in mass ratio and crystal structure to enhance reversible capacity and initial charge/discharge efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a non-aqueous electrolyte secondary battery uses lithium-nickel-manganese composite oxide with oxygen deficiency to improve initial charge/discharge efficiency, then initial charge/discharge efficiency is improved, but high capacity cannot be maintained due to unstable crystal structure
Solution Approach 1:
The patent uses a composite material consisting of Li2MO3 (layered structure) and LiMn2O4 (spinel structure) in a specific mass ratio range (70:30 to 30:70). This composite structure combines the advantages of both structures: the layered Li2MO3 provides high capacity and the spinel LiMn2O4 provides structural stability and good initial charge/discharge efficiency, thereby resolving the contradiction between initial efficiency and capacity maintenance.
Solution Approach 2:
The patent optimizes the mass ratio parameters of Li2MO3 and LiMn2O4 to achieve the best performance balance. By adjusting these compositional parameters within specific ranges, the battery achieves both high initial charge/discharge efficiency and maintained high capacity, resolving the structural stability issue while maintaining oxygen deficiency benefits.
2Quantity of substance
If cathode composition with formula LiyM1-xNixCo1-y/3Mn1-y/3O2 is used to enhance capacity characteristics, then capacity characteristics are enhanced, but discharge capacity, discharge operation voltage and initial rate characteristics are insufficient
Solution Approach 1:
The patent employs a composite cathode material consisting of Li2MO3 and LiMn2O4 in specific mass ratios. This composite structure addresses the insufficient discharge capacity and initial rate characteristics by combining the high capacity potential of Li2MO3 with the excellent rate characteristics and stable voltage profile of LiMn2O4, while maintaining improved discharge operation voltage.
Solution Approach 2:
The patent creates different local structures within the cathode material: Li2MO3 regions provide high capacity characteristics while LiMn2O4 regions provide stable discharge operation voltage and good rate characteristics. This local differentiation of material properties resolves the contradiction between capacity enhancement and discharge performance.
Data Source
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AI summary
A positive electrode active material for an electric device contains a first active material and a second active material. The first active material is composed of a transition metal oxide represented by formula (1): Li1.5[NiaCobMnc[Li]d]O3...(1) (where, in the formula (1), a, b, c and d satisfy relationships: 0<d<0.5; a+b+c+d=1.5; and 1.0<a+b+c<1.5). The second active material is composed of a spinel-type transition metal oxide represented by formula (2) and having a crystal structure belonging to a space group Fd-3m: LiMa'Mn2-a'O4...(2) (where, in the formula (2), M is at least one metal element with a valence of 2 to 4, and a' satisfies a relationship: 0≤a'<2.0). A content ratio of the first active material and the second active material satisfies, in a mass ratio, a relationship represented by expression (3): 100:0<MA:MB<0:100...(3) (where, in the formula (3), MA is a mass of the first active material, and MB is a mass of the second active material).