Lithium-Ion Battery Positive Electrode Material Design
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Solution Overview
Problem
Lithium ion secondary batteries face a trade-off between battery capacity characteristics and gas emission characteristics due to the decomposition reaction of Ni2O during charge and discharge, which affects safety and performance, and the use of metallic lithium as a compensating material is challenging due to its reactivity with moisture, increasing costs and handling difficulties.
Innovation Solution
A positive electrode active material comprising a first lithium composite oxide and a second lithium composite oxide, where the second lithium composite oxide has a larger charge capacity per unit volume and includes elements like aluminum or copper to suppress oxygen gas generation, allowing for improved battery capacity and safety by preferentially using the first oxide for subsequent charge cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Li2NiO2-based composite oxide is used to compensate for irreversible capacity, then battery capacity characteristic is improved, but oxygen gas is generated due to decomposition reaction of Ni2O, worsening gas emission characteristic and safety
Solution Approach 1:
The patent converts the harmful decomposition reaction of Ni2O that generates oxygen gas into a beneficial process by controlling it to occur preferentially during initial charge-discharge cycles. The Li2NiO2-based composite oxide sacrifices itself in the initial cycles to compensate for irreversible capacity, while the main LiCoO2正极材料 remains intact for subsequent cycles, thus converting a harmful effect into a useful capacity compensation mechanism.
Solution Approach 2:
The patent applies preliminary action by using the Li2NiO2-based composite oxide to perform the capacity compensation function during initial charge-discharge cycles before the main LiCoO2正极材料 is fully utilized. This preliminary action of capacity compensation prevents the need for excessive LiCoO2 that would otherwise require higher charging voltages and generate more oxygen gas during normal operation.
2Use of energy by moving object
If charging voltage is increased to obtain high battery capacity, then energy density is improved, but decomposition reaction of LiCoO2 is accelerated, worsening gas emission and safety
Solution Approach 1:
The Li2NiO2-based composite oxide acts as an intermediary that absorbs the harmful effects of high-voltage charging. By having this material present in the正极, it preferentially undergoes decomposition at lower voltages during initial cycles, thereby protecting the main LiCoO2正极材料 from excessive voltage stress and reducing its decomposition rate during normal high-voltage operation.
3Quantity of substance
If metallic lithium is used to compensate for irreversible capacity, then battery capacity is improved, but reactivity with moisture increases handling difficulty and cost
Solution Approach 1:
The patent uses Li2NiO2-based composite oxide as a disposable capacity compensation material that is incorporated directly into the正极 structure. Unlike metallic lithium which requires special handling and protection from moisture, this composite oxide can be safely handled during manufacturing while still providing the necessary capacity compensation function through its controlled decomposition during initial cycles.
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
This configuration breaks the trade-off between battery capacity and gas emission characteristics, enabling high battery capacity and excellent safety by using the second lithium composite oxide for initial charge and discharge to compensate for irreversible capacity and the first oxide for subsequent cycles, maintaining high energy density and reducing oxygen gas generation.
Implementation Method 1
a lithium ion secondary battery using occlusion and emission of lithium ions
Implementation Method 2
the decomposition reaction of Ni2O during charge and discharge
Data Source
AI summary
A lithium ion secondary battery including a positive electrode; a negative electrode; and an electrolytic solution, wherein the positive electrode includes a first lithium composite oxide and a second lithium composite oxide expressed by following formula (1) as a positive electrode active material, and wherein the second lithium composite oxide has a charge capacity greater than the first lithium composite oxideLi1+a(NibM1cM21−b−c)1.5−0.5aO2 (1)wherein, M1 represents at least one selected from among elements of group 13 to group 15 in an extended periodic table of elements excluding boron B, or carbon C, or nitrogen N, M2 represents at least one selected from among elements of group 3 to group 12, and a, b, and c satisfy relationships of 0.95≦a≦1.05, 0<b≦0.99, and 0<c≦0.15.