High-Nickel Lithium-Ion Cathode Coating for Low-Cobalt Resistance Control
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Solution Overview
Problem
The increasing demand for lithium ion secondary batteries for vehicles has led to concerns about cobalt depletion, and reducing cobalt content in positive electrode active materials results in significant increases in initial resistance and storage time resistance.
Innovation Solution
A lithium ion secondary battery design featuring a positive electrode with a high nickel content lithium-transition metal complex oxide, coated with a tungsten or phosphorus compound, and a negative electrode with a silicon-containing carbon material, maintaining a balanced composition to minimize cobalt usage while reducing resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the containing rate of Co in the positive electrode active material is decreased, then cobalt depletion is mitigated, but initial resistance increases significantly
Solution Approach 1:
The patent changes the chemical composition parameters of the positive electrode active material by specifying a lithium nickel manganese oxide with Ni containing rate of 75-95 mol% and controlled Mn content, while eliminating or minimizing Co. This parameter optimization allows achieving low cobalt content while maintaining acceptable resistance characteristics through the specific compositional ratio and the presence of a covering part.
Solution Approach 2:
The patent employs a composite structure consisting of a lithium nickel manganese oxide core material combined with a covering part containing tungsten compound and/or phosphorus compound. This composite material approach allows the core to provide high capacity through high Ni content while the covering part suppresses resistance increase by protecting the surface, thereby resolving the contradiction between low Co content and low resistance.
2Quantity of substance
If the containing rate of Co in the positive electrode active material is decreased, then cobalt resource sustainability is improved, but resistance at storing time increases significantly
Solution Approach 1:
The patent optimizes the compositional parameters of the lithium nickel manganese oxide by controlling the Ni containing rate within 75-95 mol% and adjusting Mn content accordingly. This parameter control ensures that the material maintains structural stability during storage without requiring high Co content, thereby reducing resistance increase at storing time while achieving cobalt reduction goals.
Solution Approach 2:
The covering part comprising tungsten compound and/or phosphorus compound forms a protective composite structure on the surface of the lithium nickel manganese oxide. This composite material configuration stabilizes the surface during storage, preventing degradation and resistance increase, thereby enabling long-term storage performance with reduced cobalt content.
3Use of energy by moving object
If high nickel content is used in the lithium-transition metal complex oxide, then energy density is improved, but material stability deteriorates
Solution Approach 1:
The patent carefully controls the compositional parameters of the lithium nickel manganese oxide, specifying Ni containing rate of 75-95 mol% while maintaining appropriate Mn content. This parameter optimization balances the high energy density contribution from Ni with the structural stability provided by Mn, preventing excessive Ni content from causing material degradation while maximizing energy storage capacity.
Solution Approach 2:
The covering part containing tungsten compound and/or phosphorus compound creates a stable composite structure where the core lithium nickel manganese oxide provides high energy density through high Ni content, while the covering part enhances overall material stability by protecting against surface degradation and maintaining structural integrity during cycling and storage.
Data Source
AI summary
In a herein disclosed lithium ion secondary battery, a positive electrode active material includes a lithium-transition metal complex oxide, containing Li, Ni, and Mn and being formed in a layered structure, and includes a covering part, a lithium-transition metal complex oxide has a Ni containing rate being equal to or more than 75 mol % with respect to the total of metal elements other than the Li and is a secondary particle consisted by a primary particle being aggregated, and the covering part contains a tungsten compound and/or a phosphorus compound. A negative electrode active material contains a carbon material and a Si containing material, and a containing ratio of a Si element in the negative electrode active material is equal to or more than 5 mass % and not more than 10 mass % when a total amount of the negative electrode active material is treated as 100 mass %.