Lithium-Ion Positive Electrode Material for High Capacity
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Solution Overview
Problem
Current lithium-ion accumulator positive electrode materials have limited reversible capacity and operating voltage, hindering the achievement of high electrochemical performance.
Innovation Solution
A compound with the formula Lia+y(M1(1−t)Mot)2M2b(O1−xF2x) is developed, where M1 is selected from Ni, Mn, Co, Fe, or V, and M2 from B, Al, Si, P, Ti, or Mo, with specific stoichiometric coefficients to enable the exchange of multiple electrons, enhancing both mass and volume capacity and operating voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If lithiated oxides of transition metals (LixMO2) are used as positive electrode material, then the material can be easily manufactured and operated, but the reversible capacity is limited to about 270 mAh/g due to single electron exchange per metal atom
Solution Approach 1:
The invention changes the oxidation state parameter of the transition metal from +3 to +2, enabling compounds like Li2NiO2 with theoretical capacity of about 510 mAh/g. This parameter change allows for two electron exchange per metal atom instead of one, effectively doubling the reversible capacity while maintaining the same material structure and manufacturing process
Solution Approach 2:
The invention uses composite materials combining transition metals (Ni, Mn, Co, Fe, V) with other elements (B, Al, Si, P, Ti, Mo) in specific stoichiometric ratios. These composite compounds like Li2Ni0.8Mn0.1Co0.1O2 achieve high reversible capacity through synergistic effects of multiple metal atoms contributing electrons, while maintaining structural stability and ease of manufacture
2Quantity of substance
If compounds based on transition metals with oxidation degree of +2 (such as Li2NiO2) are used, then the theoretical capacity increases to about 510 mAh/g, but the initial irreversible capacity is high and the operating voltage is low (less than 2V)
Solution Approach 1:
The invention applies local quality by creating non-uniform distribution of different metal atoms within the crystal structure. For example, in Li2Ni0.8Mn0.1Co0.1O2, Ni atoms provide high capacity while Mn and Co atoms stabilize the structure and reduce irreversible capacity. This local differentiation of atomic roles allows the material to achieve both high theoretical capacity and low initial irreversible capacity simultaneously
Solution Approach 2:
The invention optimizes the stoichiometric parameters of the compound to balance capacity and voltage. By adjusting the ratios of Li, transition metals, and other elements, the invention achieves compounds with operating voltage above 2.5V while maintaining high reversible capacity. The parameter optimization also reduces initial irreversible capacity by ensuring proper lithium content and metal atom distribution
3Quantity of substance
If silicates and titanates (Li2MSiO4 and Li2MTiO4) are used, then the theoretical mass capacity is improved to 330 mAh/g, but the theoretical volume capacity remains comparable to lamellar compounds with single electron exchange
Solution Approach 1:
The invention uses composite materials with transition metals having +2 oxidation state combined with other elements in specific ratios. This composite approach achieves both high mass capacity (above 510 mAh/g for Li2NiO2-type compounds) and high volume capacity by utilizing the three-dimensional crystal structure that allows efficient lithium ion insertion and extraction in all directions, unlike the layered structure of silicates and titanates
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 compound achieves a reversible mass capacity of at least 160 mAh/g and an average operating voltage of at least 2.5V, significantly improving the electrochemical performance of lithium-ion accumulators.
Implementation Method 1
the electrochemically active elements M1 and Mo, which are capable of exchanging, respectively, at least two electrons... the transition metals M1 and Mo, which are capable of passing, respectively, from the oxidation state +2 to the oxidation state +4
Implementation Method 2
lithium for which the stoichiometric coefficient is close to the number of exchangeable electrons... capable of exchanging, respectively, at least two electrons
Data Source
AI summary
A compound of formula Lia+y(M1(1−t)Mot)2M2b(O1−xF2x)c wherein:M1 is selected from the group consisting in Ni, Mn, Co, Fe, V or a mixture thereof;M2 is selected from the group consisting in B, Al, Si, P, Ti, Mo;with4≦a≦6;0<b≦1.8;3.8≦c≦14;0≦x<1;−0.5≦y≦0.5;0≦t≦0.9;b/a<0.45;the coefficient c satisfying one of the following relationships:c=4+y/2+z+2t+1.5b if M2 is selected from B and Al;c=4+y/2+z+2t+2b if M2 is selected from Si, Ti and Mo;c=4+y/2+z+2t+2.5b if M2 is P;with z=0 if M1 is selected from Ni, Mn, Co, Fe andz=1 if M1 is V.