Coated High-Nickel Cathode Material for Low-Gas Li-Ion Storage
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Solution Overview
Problem
Current positive active materials in lithium-ion batteries, such as high-nickel ternary materials, suffer from significant side reactions with the electrolyte, leading to gas production and deterioration of storage performance, while methods to reduce nickel content or residual lithium content compromise energy density and cycle performance.
Innovation Solution
A positive active material with a coating layer, Li x Ni y Co z M k Me p O r A m, is developed, where 0.85≤x≤1.15, 0.50≤y≤0.90, 0.05≤z≤0.2, 0.05≤k≤0.4, and 0≤p≤0.05, 1≤r≤2, M is selected from Mn and Al, Me from Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, and Nb, and A from N, F, S, Cl, with a particle size D n 10 of 0.5 µm≤D n 10≤3 µm, to reduce side reactions and gas production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If nickel content in the ternary material is increased to improve energy density, then energy density is improved, but side reactions with electrolyte increase significantly causing severe gas production
Solution Approach 1:
A coating layer comprising Li2SiO3 and Li4SiO4 is formed on the surface of the positive active material particles. This coating layer acts as an intermediary barrier between the high-nickel ternary material and the electrolyte, reducing direct contact and side reactions while maintaining the high nickel content (0.80 ≤ y ≤ 0.95) necessary for high energy density. The coating layer specifically suppresses gas production by preventing electrolyte decomposition at the material surface.
Solution Approach 2:
The positive active material is designed as a composite structure with a core shell configuration: a high-nickel ternary material core (Li1-xNiyCozMkMepO2-rAr) surrounded by a protective coating shell of Li2SiO3 and Li4SiO4. This composite structure allows the inner core to provide high energy density through high nickel content while the outer shell provides protection against electrolyte side reactions and gas production.
2Object-generated harmful factors
If nickel content is reduced to decrease gas production, then gas production decreases, but energy density is compromised
Solution Approach 1:
Instead of reducing nickel content, the invention introduces a coating layer of Li2SiO3 and Li4SiO4 as an intermediary that blocks the harmful interaction between high-nickel material and electrolyte. This allows maintaining high nickel content (0.80 ≤ y ≤ 0.95) for high energy density while the coating layer specifically targets and reduces gas production by preventing electrolyte decomposition.
3Quantity of substance
If washing is performed to reduce residual lithium content on the surface, then residual lithium content is reduced, but reversible capacity per gram deteriorates
Solution Approach 1:
The coating layer of Li2SiO3 and Li4SiO4 is formed on the surface of the positive active material particles before battery assembly, serving as a preliminary protective action. This pre-formed coating reduces residual lithium content on the surface without requiring aggressive washing processes that would remove active material and deteriorate reversible capacity. The coating is applied in a controlled manner to maintain particle integrity.
4Speed
If particle size is reduced to improve rate performance, then rate performance is improved, but specific surface area increases leading to more side reactions
Solution Approach 1:
The invention creates a composite structure where small particles (Dn10: 0.5-3 μm) of high-nickel ternary material are coated with Li2SiO3 and Li4SiO4. The small particle size ensures good rate performance by shortening lithium ion diffusion paths, while the coating layer compensates for the increased specific surface area by providing a protective barrier that reduces side reactions with the electrolyte.
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 effectively reduces side reactions, decreases gas production, and improves storage performance without deteriorating energy density, cycle performance, and rate performance of lithium-ion batteries.
Implementation Method 1
The positive active material is Li x Ni y Co z M k Me p O r A m whose surface is provided with a coating layer
Data Source
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AI summary
This application provides a positive active material, a positive electrode plate, an electrochemical energy storage apparatus, and an apparatus. The positive active material is LixNiyCozMkMepOrAm or LixNiyCozMkMepOrAm whose surface is provided with a coating layer. The positive active material is secondary particles, and a particle size Dn10 of the positive active material satisfies: 0.5 µm≤D.10≤3 µm. In this application, particle morphology of the positive active material and the amount of micro powder in the positive active material are properly controlled, to effectively reduce side reactions between the positive active material and an electrolyte, decrease gas production of the electrochemical energy storage apparatus, and improve storage performance of the electrochemical energy storage apparatus without deteriorating energy density, cycle performance and rate performance of the electrochemical energy storage apparatus.