Lithium Ion Battery Activation Stabilizing Solid Solution Cathode
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Solution Overview
Problem
Lithium ion batteries with solid solution positive electrode active materials, such as Li2MnO3, exhibit poor cycle durability when subjected to high charge-discharge potentials, leading to rapid deterioration.
Innovation Solution
A method for producing lithium ion secondary batteries using a negative electrode with carbon or silicon-based materials and a solid solution positive electrode active material represented by the composition Li2-xMn1+xO3, where 0 < x < 1, and M is a lithium-containing transition metal oxide with specific ratios of Ni, Co, Mn, and other elements, combined with a controlled charge-discharge process that includes repeating cycles at higher upper limit charging voltages and lower current densities, and allowing natural recovery of electromotive force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If solid solution positive electrode active material (Li2MnO3) is used to increase discharge capacity, then electric capacity exceeds 200 mAh/g, but cycle durability is poor and deterioration occurs quickly under high potential charge-discharge
Solution Approach 1:
The patent applies preliminary action by performing a specific charge-discharge treatment before the battery is put into actual use. This treatment involves charging to a high upper limit voltage (4.2V or higher) and discharging to a lower limit voltage (2.0V or lower) to preliminarily activate the solid solution positive electrode active material, stabilizing its crystal structure before high-capacity operation begins
Solution Approach 2:
The patent applies parameter changes by modifying the charge-discharge voltage parameters during the activation treatment. Specifically, it uses an upper limit charging voltage of 4.2V or higher and a lower limit discharge voltage of 2.0V or lower to induce structural changes in the positive electrode material, transforming it from an unstable state to a stable state that can sustain high capacity operation
2Quantity of substance
If charge-discharge is carried out at high potential to maximize capacity utilization, then electric capacity is maximized, but the positive electrode active material deteriorates rapidly
Solution Approach 1:
The patent performs preliminary activation treatment with extreme voltage parameters (4.2V+ charging, 2.0V- discharging) before normal operation to prepare the positive electrode material for sustained high-capacity cycling without rapid deterioration
Solution Approach 2:
The patent applies preliminary anti-action by using the extreme charge-discharge treatment to counteract and prevent the rapid deterioration that would otherwise occur during high-potential operation, effectively pre-stabilizing the material against degradation
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 approach stabilizes the crystal structure of the positive electrode, suppressing battery deterioration and maintaining high capacity even under high potential charge-discharge conditions.
Implementation Method 1
stabilizes the crystal structure of the positive electrode, suppressing battery deterioration
Implementation Method 2
repeating charge-discharge multiple times, wherein the upper limit charging voltage is the same as or higher than the immediately prior charge-discharge interval
Data Source
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Figure 3(a)~3(b)
AI summary
[Object] To provide a method for producing a secondary battery that is high-capacity and that suppresses deterioration in charge-discharge at a high potential. [Solution] A method for producing a lithium ion secondary battery comprising the positive electrode active material of formula (1), Li(2-0.5x)Mn1-xM1.5xO3 (x satisfies 0 < x < 1)...(1) (M in the formula is a lithium-containing transition metal oxide expressed by NiaCobMncMld (in which 0 < ≤ 0.5, 0 ≤ b ≤ 0.33, 0 < c ≤ 0.5, and 0 ≤ d ≤ 0.1 are satisfied, the sum of a, b, c, and d becomes 1, and M1 in the formula is an element selected from Li, V, Al, Zr, Ti, Nb, Fe, Cu, Cr, Mg, and Zn)). The method comprises a step to repeat charge-discharge multiple times (charge-discharge interval), and comprises a step to discharge a at a lower current density than the current density during charge a, during the discharge of the multiple charges-discharges, or, a step to discharge b at a lower current density than the current density during charge a after the electromotive force is naturally recovered by idle b after each charge-discharge.