Gradient Lithium Metal Oxide Cathode for High Nickel Safety
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Solution Overview
Problem
Lithium metal oxide (LMO) cathodes with high nickel content in lithium ion batteries suffer from short cycle life, safety issues due to oxygen evolution, and inconsistencies in performance, while existing synthesis methods face challenges in producing single-phase layered materials and require large capital investment and long reaction times.
Innovation Solution
A method involving a precursor mixture of Li, Ni, Co, and Mn particulates with controlled primary particle sizes, agglomerated to form secondary particles, then heated in an oxygen-containing atmosphere to create a lithium metal oxide with a specific primary particle size and chemical composition, achieving a safer gradient structure and increased energy capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high nickel content is used in LMO cathodes to increase energy capacity, then energy density is improved, but safety issues arise due to oxygen evolution and cycle life decreases
Solution Approach 1:
The patent applies local quality by creating a gradient structure where the particle core contains high nickel content (0.6-0.8 mole fraction) for high energy capacity, while the particle surface has reduced nickel content (0.3-0.5 mole fraction) to improve stability and safety. This spatial variation in composition allows simultaneous optimization of energy density and reliability.
2Ease of manufacture
If solid state synthesis is used to make LMO, then material can be produced, but difficulty in making single phase layered material and requirement for very small size particles occurs
Solution Approach 1:
The patent applies preliminary action by pre-forming particles with controlled size distribution (D50 of 3-10 micrometers) and specific morphology before the solid state synthesis reaction. This pre-preparation of precursors with optimal characteristics enables successful formation of single phase layered LMO structure during subsequent heating, avoiding the need for extremely small particles.
3Productivity
If continuous stirred reactors are used for precipitation to make LMO, then production can be scaled, but long reaction residence times and large capital investment are required
Solution Approach 1:
The patent applies copying by using spray drying to create precursor particles that replicate the desired final particle size distribution and morphology. This copying approach allows direct formation of particles with optimal dimensions (D50 of 3-10 micrometers) without requiring long residence times in continuous stirred reactors, thereby reducing both time loss and capital investment while maintaining production scalability.
4Ease of manufacture
If precipitation process is used to form LMO, then complex metal compounds can be processed, but low cathode density and low safety particularly for high Ni compositions result
Solution Approach 1:
The patent applies parameter changes by controlling the spray drying process parameters (inlet temperature, outlet temperature, feed rate) to produce precursor particles with specific characteristics (size distribution, morphology, composition). These parameter-controlled precursors then yield LMO with high cathode density and improved safety after solid state synthesis, while still enabling processing of complex high nickel compositions.
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 method results in LMOs with improved safety, higher cycle life, and energy density, maintaining good rate capability and allowing for the production of highly dense cathodes with increased battery capacity without compromising other desirable battery characteristics.
Implementation Method 1
heating the secondary particles under an oxygen containing atmosphere to a maximum temperature of from 930 °C to 960 °C and for a time to form the lithium metal oxide
Data Source
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AI summary
A method for forming lithium metal oxides comprised of Ni, Mn and Co useful for making lithium ion batteries comprises providing precursor particulates of Ni and Co that are of a particular size that allows the formation of improved lithium metal oxides. The method allows the formation of lithium metal oxides having improved safety while retaining good capacity and rate capability. In particular, the method allows for the formation of lithium metal oxide where the primary particle surface Mn/Ni ratio is greater than the bulk Mn/Ni. Likewise the method allows the formation of lithium metal oxides with secondary particles having much higher densities allowing for higher cathode densities and battery capacities while retaining good capacity and rate performance.