Lithium Transition Metal Oxide Crystallinity via Organic Flux
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Solution Overview
Problem
Current methods for producing lithium-containing transition metal oxides for lithium secondary batteries face challenges with high Ni content compounds, where the use of lithium hydroxide is costly, and lithium carbonate results in low crystallinity due to higher reaction temperatures, leading to reduced battery performance.
Innovation Solution
A method involving mixing a transition metal compound with Ni and M with lithium carbonate, then heating the mixture in a rotary kiln with alternating temperature cycles to promote crystal growth, using lithium carbonate with a mean particle size of 6 μm or less, and further heating to enhance crystallinity, allowing for high Ni content lithium-containing transition metal oxides with improved structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If lithium carbonate is used as the lithium compound to reduce production costs, then manufacturing cost is reduced, but the reaction temperature increases by approximately 200°C compared to lithium hydroxide, leading to reduced crystallinity and poor active material characteristics
Solution Approach 1:
The patent applies preliminary action by pre-mixing lithium carbonate with a organic compound (such as citric acid, ethylene diamine tetraacetic acid, or glucose) before the reaction with the transition metal compound. This pre-mixture serves as a flux that lowers the reaction temperature and promotes uniform crystal growth, thereby achieving high crystallinity despite using the cheaper lithium carbonate instead of lithium hydroxide
Solution Approach 2:
The organic compound acts as an intermediary substance between lithium carbonate and the transition metal compound. It facilitates the reaction by forming a complex with the transition metal ions, enabling the reaction to proceed at lower temperatures and producing a more uniform and crystalline product structure
2Quantity of substance
If high Ni content transition metal compound is used to achieve high discharge capacity, then energy density is improved, but Ni3+ ions are reduced to Ni2+ and included in the lithium site at higher temperatures, resulting in low crystallinity and reduced active material characteristics
Solution Approach 1:
The patent uses preliminary action by pre-complexing the high Ni content transition metal compound with an organic compound before reaction with lithium carbonate. This pre-complexation stabilizes the Ni3+ ions and prevents their reduction to Ni2+ during the reaction, even at elevated temperatures, thereby maintaining high crystallinity and preventing Ni ion inclusion in the lithium site
Solution Approach 2:
The patent applies parameter changes by modifying the chemical environment through the addition of organic compounds that change the reaction kinetics and thermodynamics. This allows the reaction to proceed at temperatures that maintain Ni3+ stability while still enabling complete reaction and high crystallinity formation
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 produces lithium-containing transition metal oxides with high crystallinity and high Ni content, suitable for use in lithium secondary batteries, enhancing their performance as positive electrode active materials by maintaining structural stability during charge/discharge cycles.
Implementation Method 1
heating the mixture to react the transition metal compound with the lithium compound
Implementation Method 2
heating the mixture in a rotary kiln with alternating temperature cycles to promote crystal growth
Implementation Method 3
promote crystal growth, using lithium carbonate with a mean particle size of 6 μm or less, and further heating to enhance crystallinity
Data Source
AI summary
A method for producing a lithium-containing transition metal oxide represented by the general formula: Li[Lix(NiaM1−a)1−x]O2 where M is metal other than Li and Ni, 0≦x, and 0<a. The method includes: (i) mixing a transition metal compound containing Ni and M in a molar ratio of a:(1−a) with lithium carbonate in a predetermined ratio; (ii) causing the temperature of the mixture to reach a predetermined temperature range while repeatedly raising and lowering the temperature thereof; and (iii) thereafter reacting the transition metal compound with the lithium carbonate in the predetermined temperature range.