Ni-Rich Cathode Coating for Thermal Stability
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries, such as lithium-ion batteries, face challenges with thermal runaway, where a charged battery self-heats at high temperatures, and existing techniques like surface-modified lithium nickel composite oxides and boric acid deposition do not adequately improve heat resistance.
Innovation Solution
A positive electrode active material with lithium-transition metal composite oxide containing 80 mol% Ni and 0.1 to 1.5 mol% B, where elements from Groups 4 to 6 are present on the surfaces of smaller particles, forming an oxide coating film that enhances heat resistance by reacting with Li and B at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If surface-modified lithium nickel composite oxide is used to suppress impedance increase, then battery impedance stability improves, but heat resistance remains insufficient
Solution Approach 1:
The invention uses a composite oxide structure where lithium nickel composite oxide particles are coated with a layer containing lithium, M1 (Groups 4-6 element), and B. This composite structure combines the high capacity of lithium nickel oxide with the heat resistance and surface stability provided by the coating layer containing M1 and B, thereby achieving both impedance stability and improved heat resistance simultaneously.
Solution Approach 2:
The invention applies different compositional qualities to different regions: the core particles contain high Ni content (80 mol% or more) for high capacity, while the surface coating layer contains M1 and B elements specifically for heat resistance and surface stability. This local differentiation of material properties allows the battery to achieve both high energy density and improved thermal safety.
2Object-generated harmful factors
If boric acid compound is deposited on particle surfaces to suppress gas generation, then electrolyte decomposition is reduced, but heat resistance improvement is insufficient
Solution Approach 1:
The coating layer is designed as a composite containing three key components: lithium (for conductivity and structural integrity), M1 from Groups 4-6 (for heat resistance and surface stability), and B (boron, for suppressing electrolyte decomposition). This tri-component composite structure provides synergistic effects that simultaneously address gas suppression and heat resistance, overcoming the limitations of boric acid deposition alone.
Solution Approach 2:
The coating layer acts as an intermediary barrier between the lithium nickel composite oxide particles and the electrolyte. This intermediate layer prevents direct contact and harmful reactions at the particle surface, suppressing electrolyte decomposition and gas generation while also providing thermal stability to improve overall heat resistance.
3Use of energy by moving object
If high Ni content (80 mol% or more) is used to achieve high energy density, then battery capacity increases, but surface stability and heat resistance deteriorate
Solution Approach 1:
The invention concentrates the high Ni content (80 mol% or more) in the core particles to maximize energy density, while concentrating the heat-resistant M1 and B elements in the surface coating layer to provide thermal stability. This spatial separation of functional properties allows the battery to achieve high energy density without sacrificing surface stability or heat resistance.
Solution Approach 2:
The battery material is structured as a composite system where high-Ni core particles provide energy density and the M1-B-containing coating layer provides thermal stability. This composite architecture allows the contradictory requirements of high Ni content for energy and surface stability for heat resistance to be satisfied simultaneously in different parts of the same material system.
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 proposed solution significantly improves the heat resistance of non-aqueous electrolyte secondary batteries by forming a conductive oxide coating film on the surface of smaller particles, which suppresses electrolyte decomposition and enhances particle strength, thereby preventing thermal runaway.
Implementation Method 1
B and at least one element (M1) selected from Groups 4 to 6 are present on at least the surfaces of particles of the composite oxide... forming an oxide coating film that enhances heat resistance by reacting with Li and B at high temperatures
Implementation Method 2
forming a conductive oxide coating film on the surface of smaller particles, which suppresses electrolyte decomposition
Data Source
AI summary
An advantage is to provide a non-aqueous electrolyte secondary battery with improved heat resistance. A positive electrode active material contains a lithium-transition metal composite oxide containing 80 mol % or more of Ni and 0.1 mol % to 1.5 mol % of B on the basis of the total number of moles of metal elements excluding Li, and B and at least one element (M1) selected from Groups 4 to 6 are present on at least the surfaces of particles of the composite oxide. When particles having a volume-based particle size larger than 70% particle size (D70) are first particles, and particles having a volume-based particle size smaller than 30% particle size (D30) are second particles, the molar fraction of M1 on the basis of the total number of moles of metallic elements excluding Li on the surfaces of the second particles is greater than that of the first particles.