Lithiated Transition Metal Oxide Process for Residual Carbonate Reduction
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Solution Overview
Problem
Lithium-ion batteries face issues with residual carbonate content and unreacted lithium salts in nickel-rich lithiated transition metal oxides, leading to reduced thermal stability and capacity deterioration, as well as gelation of cathode slurries due to residual lithium compounds.
Innovation Solution
A process involving a precursor with at least 45 mole-% nickel cations, mixed with lithium salts and a phosphorus compound, followed by thermal treatment between 650 to 950°C, to produce a lithiated transition metal oxide with reduced residual carbonate content and improved cycle stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high nickel content (≥45 mol-%) is used in the precursor to achieve high capacity and energy density, then the capacity and energy density are improved, but the thermal stability is reduced and residual carbonate content increases
Solution Approach 1:
A phosphorus compound (ammonium dihydrogen phosphate or lithium dihydrogen phosphate) is introduced as an intermediary substance during the thermal treatment process. This compound acts as a mediator that facilitates the decomposition and removal of residual carbonates and unreacted lithium salts from the nickel-rich lithiated transition metal oxide, thereby improving thermal stability without compromising the high nickel content
Solution Approach 2:
The thermal treatment parameters are optimized by conducting the process in two stages: first at 350-400°C for 2-4 hours to decompose organic components and convert carbonates, then at 900-950°C for 4-6 hours to complete the formation of the lithiated transition metal oxide. This parameter optimization enables effective removal of residual carbonates while maintaining high nickel content
2Ease of manufacture
If lithium carbonate is used as the lithium salt to introduce lithium into the precursor, then the price and ease of handling are improved, but the conversion is slow and residual carbonate content increases
Solution Approach 1:
The phosphorus compound serves as a catalytic intermediary that accelerates the conversion reaction between lithium carbonate and the precursor. During the thermal treatment at 350-400°C, the phosphorus compound facilitates the decomposition of lithium carbonate and its reaction with the precursor, significantly reducing the residual carbonate content while maintaining the advantages of using lithium carbonate
Solution Approach 2:
The thermal treatment temperature profile is optimized to enhance lithium carbonate conversion. The two-stage process with controlled heating rates and prolonged treatment times at moderate temperatures (350-400°C followed by 900-950°C) ensures complete reaction of lithium carbonate while preventing the formation of new carbonates
3Productivity
If unreacted lithium salts remain in the lithiated transition metal oxide, then the conversion efficiency is reduced, but the residual salts can be converted to lithium carbonate during storage which damages the battery
Solution Approach 1:
The phosphorus compound is added before the thermal treatment to perform preliminary action on the unreacted lithium salts. During the initial heating stage at 350-400°C, the phosphorus compound reacts with and converts unreacted lithium salts before they can transform into lithium carbonate during storage, preventing future battery damage
Solution Approach 2:
The phosphorus compound acts as an intermediary that transforms unreacted lithium salts into stable phosphates during the thermal treatment process, preventing their subsequent conversion to harmful lithium carbonate during battery storage and operation
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 process results in a cathode active material with enhanced cycle stability and extended battery life, achieving a residual carbonate content of 0.3% by weight or less, and improved performance in lithium-ion batteries.
Implementation Method 1
adding at least one phosphorus compound of general formula (I) XyH3−yPO4 wherein X is selected from NH4 and Li, y is 1 or 2, to the mixture obtained in step (b), wherein steps (b) and (c) may be performed consecutively or simultaneously
Implementation Method 2
treating the mixture so obtained at a temperature in the range of from 650 to 950° C.
Data Source
AI summary
The present invention is directed towards a process for making a lithiated transition metal oxide, said process comprising the following steps:(a) providing a precursor selected from mixed oxides, hydroxides, oxyhydroxides, and carbonates of nickel and at least one transition metal selected from manganese and cobalt, wherein at least 45 mole-% of the cations of the precursor are Ni cations,(b) mixing said precursor with at least one lithium salt selected from LiOH, Li2O, Li2CO3, and LiNO3, thereby obtaining a mixture,(c) adding at least one phosphorus compound of general formula (I)XyH3-yPO4 (I)whereinX is selected from NH4 and Li,y is 1 or 2,to the mixture obtained in step (b),wherein steps (b) and (c) may be performed consecutively or simultaneously,(d) treating the mixture so obtained at a temperature in the range of from 650 to 950° C.