High-Nickel Cathode Coating Structure for Safer Secondary Batteries
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Solution Overview
Problem
Secondary batteries face safety concerns due to inadequate safety features, necessitating the development of a configuration that enhances safety without compromising battery capacity.
Innovation Solution
A secondary battery design featuring a positive electrode with a layered rock salt type lithium composite oxide containing nickel, fluorine, and boron, along with a fluorine-containing lithium salt in the electrolyte, where the positive electrode active material layer includes a central portion and a covering portion with lithium, fluorine, and boron, and a fluorine-containing lithium salt in the electrolyte, detected using time-of-flight secondary ion mass spectrometry, ensuring a specific ionic strength peak distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a high-nickel lithium composite oxide is used in the positive electrode active material, then battery capacity is improved, but safety deteriorates due to excessive temperature rise and potential ignition
Solution Approach 1:
The positive electrode active material is segmented into a central portion containing high-nickel lithium composite oxide (LiNi0.85Co0.05Mn0.10O2) and a covering portion containing lithium, fluorine, boron, and oxygen. This segmentation allows the core to maintain high capacity while the surface layer provides safety protection by suppressing excessive temperature rise and preventing ignition.
Solution Approach 2:
The patent uses a composite material structure where the central portion contains lithium nickel cobalt manganese oxide with 80-100 mol% nickel, and the covering portion contains lithium, fluorine, boron, and oxygen. The fluorine-containing lithium salt in the electrolyte (such as LiPF6, LiBF4, or LiDFB) further contributes to the composite system, creating a multi-layered protective structure that maintains battery capacity while enhancing safety.
2Reliability
If fluorine and boron are incorporated into the lithium composite oxide structure, then safety is improved by suppressing temperature rise, but manufacturing complexity increases
Solution Approach 1:
The fluorine and boron are incorporated into the covering portion of the positive electrode active material before battery assembly. The covering portion contains lithium, fluorine, boron, and oxygen, which are preliminarily structured to suppress temperature rise during battery operation. This preliminary action simplifies manufacturing by pre-configuring the safety mechanism rather than requiring post-assembly modifications.
Solution Approach 2:
The patent specifies precise compositional parameters: the lithium composite oxide contains 80-100 mol% nickel, and the covering portion contains specific elements (lithium, fluorine, boron, oxygen). The fluorine-containing lithium salt in the electrolyte is selected from specific compounds (LiPF6, LiBF4, LiDFB). These parameter specifications standardize the manufacturing process while achieving the desired safety performance.
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 achieves excellent safety by suppressing excessive temperature rise and preventing potential ignition, while maintaining high battery capacity and stability.
Implementation Method 1
a first negative secondary ion derived from LiF2− and a second negative secondary ion derived from BO2− are detected in analysis in a depth direction of the positive electrode active material layer using time-of-flight secondary ion mass spectrometry
Implementation Method 2
a first negative secondary ion derived from LiF2− and a second negative secondary ion derived from BO2− are detected in analysis in a depth direction of the positive electrode active material layer using time-of-flight secondary ion mass spectrometry
Data Source
AI summary
A secondary battery is provided and includes a positive electrode including a positive electrode active material layer, a negative electrode, and an electrolytic solution including an electrolyte salt. The positive electrode active material layer includes a plurality of positive electrode active material particles, and the positive electrode active material particles each include a central portion including a lithium composite oxide and a covering portion provided on a surface of the central portion. The lithium composite oxide has a crystal structure of a layered rock salt type and includes lithium, nickel, and other elements as constituent elements. The covering portion includes lithium, fluorine, boron, and oxygen as constituent elements. The electrolyte salt includes a fluorine-containing lithium salt. When a sum of a content of the nickel in the lithium composite oxide and a content of the other elements in the lithium composite oxide is taken as 100 parts by mol, the content of the nickel in the lithium composite oxide is 80 parts by mol or more and 100 parts by mol or less. A first negative secondary ion derived from LiF2− and a second negative secondary ion derived from BO2− are detected in analysis in a depth direction of the positive electrode active material layer using time-of-flight secondary ion mass spectrometry. A change in ionic strength of the first negative secondary ion in the depth direction has a first peak, and a change in ionic strength of the second negative secondary ion in the depth direction has a second peak. The second peak is located on a deeper side than the first peak in the depth direction.