Lithium Transition Metal Composite Oxide for Battery Internal Resistance
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Solution Overview
Problem
Nonaqueous electrolyte energy storage devices using lithium-excess-type active materials for positive electrodes experience an increase in internal resistance during charge-discharge cycles, which affects their performance and capacity retention.
Innovation Solution
Incorporating a lithium transition metal composite oxide with an α-NaFeO2 structure, containing nickel, cobalt, and manganese, and aluminum, and limiting the initial charge-discharge potential to less than 4.5 V vs. Li/Li+ to prevent crystal structure changes that contribute to increased internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If initial charge-discharge is performed until the positive electrode potential reaches 4.5 V vs. Li/Li+ or more to activate lithium-excess-type active material, then the discharge capacity increases, but the internal resistance increases with charge-discharge cycles
Solution Approach 1:
The patent specifies precise compositional parameters for the lithium transition metal composite oxide, including Li content (1.05-1.30), Mn content (0.20-0.60), Ni content (0.10-0.50), and Al content (0.05-0.30), along with a specific XRD diffraction peak position (20°-22°). These parameter controls optimize the crystal structure to enable high discharge capacity while maintaining internal resistance stability during cycling.
Solution Approach 2:
The patent uses a composite lithium transition metal composite oxide containing multiple elements (Li, Mn, Ni, Al) in specific ratios. This composite material combines the high capacity benefits of lithium-excess composition with the structural stability provided by Mn, Ni, and Al, resolving the contradiction between capacity and cycle stability.
2Quantity of substance
If high lithium content (Li/Me > 1) is used to increase discharge capacity, then the energy density improves, but the crystal structure becomes unstable leading to increased internal resistance
Solution Approach 1:
The patent creates a composite lithium transition metal composite oxide where excess lithium is balanced by stabilizing elements (Mn, Ni, Al). The specific composition ranges ensure high lithium content for capacity while the multi-element composite structure maintains crystal stability during charge-discharge cycles.
Solution Approach 2:
The patent optimizes the local composition within the crystal structure by controlling the distribution of different elements. The specific ratios of Li, Mn, Ni, and Al create local structural environments that stabilize the crystal lattice while maintaining high lithium content for capacity.
3Ease of manufacture
If manganese is used as the transition metal to reduce cost and improve availability, then the manufacturing cost decreases, but manganese elution occurs during cycling increasing internal resistance
Solution Approach 1:
The patent uses a composite material containing Mn along with Ni and Al. The Ni and Al elements act as structural stabilizers that prevent Mn elution during cycling, while Mn provides cost benefits and contributes to capacity. This composite approach resolves the contradiction between cost and stability.
Solution Approach 2:
The Ni and Al elements serve as intermediary stabilizers that protect the Mn from elution. These elements mediate between the cost benefits of Mn and the stability requirements, preventing Mn loss while maintaining the cost advantages of using abundant manganese.
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
This approach suppresses the increase in internal resistance and maintains a high capacity retention ratio by preventing lithium ion diffusion rate decreases and manganese elution, allowing for stable and efficient energy storage.
Implementation Method 1
a diffraction peak is present in a range of 200 or more and 220 or less in an X-ray diffraction diagram of the lithium transition metal composite oxide using a CuKα ray
Data Source
AI summary
A nonaqueous electrolyte energy storage device according to one aspect of the present invention is a nonaqueous electrolyte energy storage device including a positive electrode having positive active material particles, in which the positive active material particles contain a lithium transition metal composite oxide having an α-NaFeO2 structure, the lithium transition metal composite oxide contains at least one of nickel and cobalt, and manganese, a content of lithium with respect to a transition metal in the lithium transition metal composite oxide exceeds 1.0 in terms of a molar ratio, a diffraction peak is present in a range of 20° or more and 22° or less in an X-ray diffraction diagram of the lithium transition metal composite oxide using a CuKα ray, and the positive active material particles contain aluminum.