Lithium-Ion Cell Mix Using Crystal-Structured Ternary Cathodes
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Solution Overview
Problem
Lithium-ion secondary batteries face limitations in comprehensive performance, including energy density, cycling performance, storage performance, and safety performance, particularly due to the restricted improvements in electrode structures that only consider layering of electrode sheets without optimizing the crystal structures of positive-electrode active materials.
Innovation Solution
The battery design incorporates bare battery cells with a combination of single crystal or single crystal-like low-nickel ternary positive electrode material and polycrystalline high-nickel ternary positive electrode material, strategically arranged to leverage the crystal lattice shrinkage properties and optimize the proportion of materials for enhanced performance, with the polycrystalline high-nickel material acting as a buffer to mitigate expansion forces and improve electrolyte infiltration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If only layering of electrode sheets is considered for improvement, then manufacturing simplicity is maintained, but comprehensive battery performance (energy density, cycling performance, storage performance, gas production performance, and safety performance) is limited
Solution Approach 1:
The patent applies local quality by using different positive electrode active materials with different crystal structures (single crystal vs. polycrystalline) in different battery cells within the same battery pack. Specifically, battery cells 1 to m-1 use single crystal or single crystal-like low-nickel ternary positive electrode material, while battery cell m uses polycrystalline high-nickel ternary positive electrode material. This localized differentiation optimizes specific parameters (cycling performance for single crystal, energy density for polycrystalline) in specific regions while maintaining overall system performance.
Solution Approach 2:
The patent employs composite materials by combining single crystal or single crystal-like low-nickel ternary positive electrode material and polycrystalline high-nickel ternary positive electrode material in a hybrid configuration. This composite approach leverages the advantages of both crystal structures: the single crystal structure provides excellent cycling performance and stability, while the polycrystalline structure delivers high energy density. The composite material strategy resolves the contradiction by achieving comprehensive performance improvement without significantly increasing manufacturing complexity.
2Quantity of substance
If polycrystalline high-nickel ternary positive electrode material is used to improve energy density, then energy density increases, but crystal lattice expansion occurs under high SOC delithiation state which affects cycling performance
Solution Approach 1:
The patent applies the counterweight principle by using single crystal or single crystal-like low-nickel ternary positive electrode material (with stable crystal structure and low expansion) to counterbalance the lattice expansion caused by polycrystalline high-nickel ternary positive electrode material. The single crystal cells are positioned in battery cells 1 to m-1, while the polycrystalline high-nickel cells are placed in battery cell m, creating a compensatory effect that stabilizes overall cycling performance while maintaining high energy density.
Solution Approach 2:
The patent changes the crystal structure parameter of the positive electrode active material from polycrystalline to single crystal or single crystal-like structure in specific battery cells. This parameter change fundamentally alters the material's response to delithiation: single crystal structures exhibit minimal lattice expansion under high SOC conditions, thereby improving cycling performance. By controlling this structural parameter in a selective manner across different battery cells, the patent achieves both high energy density and excellent cycling stability.
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 configuration significantly enhances the lithium-ion battery's comprehensive performance by improving energy density, cycling stability, gas production, and safety, while avoiding issues like lithium plating and cyclic diving, through optimized material proportions and structural arrangements.
Implementation Method 1
the relatively more obvious crystal lattice shrinkage property of the polycrystalline high-nickel ternary positive electrode material under a high SOC (state of charge) delithiation state
Data Source
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AI summary
The present invention relates to the field of electrochemistry, and in particular to a lithium-ion secondary battery, a battery module, a battery pack, and a powered device. The present invention provides a lithium-ion secondary battery, which includes a bare battery cell accommodating cavity in which a bare battery cell group including one or more bare battery cells A and one or more bare battery cells B is arranged, wherein the bare battery cell A includes a first positive electrode sheet including a first positive-electrode active material selected from a single crystal or single crystal-like low-nickel ternary positive electrode material A1, the bare battery cell B includes a second positive electrode sheet including a second positive-electrode active material and/or a third positive-electrode active material, the second positive-electrode active material is selected from a polycrystalline high-nickel ternary positive electrode material B1, and the third positive-electrode active material is selected from a polycrystalline low-nickel ternary positive electrode material B2. The lithium-ion battery provided by the present invention has excellent cycle, storage, gas production, and safety performance under high energy density and high state of charge.