Nonaqueous Battery Electrolyte for Low-Co Cathode Cycle Stability
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Solution Overview
Problem
The increasing cost of Co in lithium-transition metal composite oxides for nonaqueous electrolyte secondary batteries leads to deterioration in cycle characteristics due to unstable lattice structures and side reactions, especially when Co content is reduced.
Innovation Solution
A nonaqueous electrolyte secondary battery design featuring a positive electrode active material with high Ni and Al content, and minimal Co, combined with an oxalate compound and an organosilicon compound in the electrolyte to stabilize the crystal structure and suppress metal leaching, thereby enhancing ionic conductivity and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Co content is reduced in lithium-transition metal composite oxide, then cost is reduced, but cycle characteristics deteriorate due to unstable lattice structure
Solution Approach 1:
The patent changes the compositional parameters by precisely controlling the atomic ratios of Ni, Mn, and Al in the lithium-transition metal composite oxide. By setting Ni to 50-80 atom%, Mn to 5-30 atom%, and Al to 5-30 atom%, the lattice structure stability is improved while maintaining low Co content (0-5 atom%), thus resolving the contradiction between cost reduction and cycle characteristics
Solution Approach 2:
The patent uses a composite material approach by combining multiple transition metals (Ni, Mn, Al) in specific ratios within the lithium oxide matrix. This composite structure provides both cost advantage (low Co) and performance (stable lattice through synergistic metal combinations), resolving the technical contradiction
2Quantity of substance
If Ni content is increased to reduce cost, then capacity increases, but lattice structure becomes unstable and side reactions increase
Solution Approach 1:
The patent optimizes the Ni content parameter to 50-80 atom%, which is high enough to provide capacity but controlled within a range that maintains lattice stability. This parameter optimization resolves the contradiction between increasing Ni for cost/capacity and maintaining structural stability
Solution Approach 2:
The patent introduces Al at 5-30 atom% specifically to stabilize the local lattice structure around high-Ni regions. This local quality adjustment (adding Al) allows high Ni content while preventing lattice instability and side reactions
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 ensures excellent cycle characteristics and reduced internal resistance, even with low Co content or Co-free lithium-transition metal composite oxides, by forming a surface film that inhibits metal leaching and side reactions.
Implementation Method 1
forming a surface film that inhibits metal leaching and side reactions
Implementation Method 2
the nonaqueous electrolyte contains an oxalate compound... by forming a surface film
Implementation Method 3
enhancing ionic conductivity... the oxalate compound contains a lithium cation and an oxalate complex anion
Data Source
AI summary
A nonaqueous electrolyte secondary battery includes a positive electrode, a negative electrode, and a nonaqueous electrolyte. The positive electrode includes a positive electrode active material, and the positive electrode active material includes a lithium-transition metal composite oxide containing Ni, Mn, and Al. The proportions of Ni, Mn, and Al in metal elements other than Li contained in the lithium-transition metal composite oxide are, respectively, Ni: 50 atm % or more, Mn: 10 atm % or less, and Al: 10 atm % or less. When the lithium-transition metal composite oxide contains Co, the proportion of Co in the metal elements other than Li is 1.5 atm % or less. The nonaqueous electrolyte contains an oxalate compound, and the oxalate compound contains a lithium cation and an oxalate complex anion.