LNCO-LNMCO Blended Cathode with Phosphate Coating
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Solution Overview
Problem
Lithium nickel cobalt oxide (LNCO) cathode materials in lithium-ion batteries suffer from thermal runaway due to oxidation of organic electrolytes at high temperatures, limiting their use in high-energy applications like consumer electronics and power tools, despite their high specific capacity and rate capability.
Innovation Solution
A blended positive electrode material combining lithium nickel cobalt oxide (LNCO) and lithium nickel manganese cobalt oxide (LNMCO) with aluminum substitution, which maintains high capacity while enhancing thermal stability by reducing oxygen release during thermal decomposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If lithium nickel cobalt oxide (LNCO) is used as cathode material, then high specific capacity and high rate capability are achieved, but thermal runaway occurs due to oxidation of organic electrolyte at high temperatures
Solution Approach 1:
The patent uses a composite material system consisting of a core shell structure where an LNCO core is coated with a lithium phosphate-based protective layer. This composite structure allows the high-capacity LNCO core to be protected by the thermally stable phosphate coating, preventing direct contact between the LNCO and electrolyte at high temperatures while maintaining electrochemical performance.
Solution Approach 2:
The lithium phosphate-based coating acts as an intermediary layer between the LNCO cathode material and the organic electrolyte. This intermediate protective layer prevents direct oxidation reactions between the LNCO and electrolyte at elevated temperatures, thereby preventing thermal runaway while allowing ion transport during normal operation.
2Reliability
If lithium nickel manganese cobalt oxide (LNMCO) is used to enhance thermal stability, then oxygen release during thermal decomposition is decreased, but specific capacity is reduced compared to LNCO
Solution Approach 1:
The patent creates a composite structure where high-capacity LNCO material is combined with a protective phosphate coating that provides thermal stability. This allows the system to achieve both high specific capacity from the LNCO core and thermal stability from the phosphate layer, avoiding the need to use lower-capacity LNMCO materials.
Solution Approach 2:
The protective phosphate coating is applied locally on the surface of the LNCO particles, creating a zone of enhanced thermal stability only where needed for protection. The bulk LNCO material retains its high-capacity properties, thus achieving local optimization without sacrificing overall 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
The blended material achieves high specific capacity, cycling efficiency, and improved thermal stability, making it suitable for high-energy density non-aqueous electrolyte lithium secondary batteries, addressing safety concerns associated with LNCO.
Implementation Method 1
LNMCO, Its addition derivatives, and LNCO materials all have a layered structure or a tunnel structure capable of absorbing or desorbing (intercalating or deintercalating) lithium ions in a reversible manner
Implementation Method 2
LNCO at temperatures of approximately 200°C or higher, and when in the charged state, can oxidize the organic electrolyte in an LIB cell, resulting in thermal runaway or degradation of the battery components. This undesirable oxidation is due to the release of oxygen from the Ni 4+
Data Source
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AI summary
A positive electrode materia! is provided which is a blended combination of lithium nickel cobalt oxide (and aluminum substituted compounds thereof) and lithium nickel manganese cobalt oxtde. Also provided Is a non-aqueous electrolyte lithium secondary battery having high specific capacity and good thermal stability characteristics.