Stabilizing high-voltage LCO cycling is a hot topic in both academic and industrial research. [3,4] However, the exact mechanism that caused the quick fading of high-voltage LCO has not yet reached consensus. [5,6] The band energy diagram in Figure S1 in the Supporting Information shows that cycling LCO to high voltage must entail a hybrid O anion (O 2− →O α− , α < 2) and Co cation-redox (HACR). [7,8] It is tempting to "exploit" HACR in LCO for much higher capacity, e.g., if LCO is charged to above 4.6 V, more than 220 mAh g −1 can be obtained; however, because of the reduced ionic radius and electrostatic force, the oxidized O α− would become much mobile [9] and more likely to escape from the particle, resulting in oxygen loss (OL). Continuous OL can be a killer problem to high-voltage cycling. [10] First, OL causes irreversible phase transformations (CoO 2 →Co 3 O 4) [11] (Figure S2, Supporting As the pioneer cathode for rechargeable Li-ion battery, [1] LiCoO 2 (LCO) is still dominating today's battery markets in consumer electronic devices, due to its high volumetric energy density and stable cycling. However, as LCO is only cycled within 4.35 V and 165 mAh g −1 at the present to meet the industrial-level cycling life, [2] there is still a large space to increase its utilizable capacity by charging LCO to higher voltages before it reaches

Grain boundary management is critical to the performance and stability of polycrystalline perovskite solar cells (PSCs), especially large-area devices. However, typical passivators are insulating in nature and limit carrier transport. Here, we design a supramolecular binder for grain boundaries to simultaneously passivate defects and promote hole transport across perovskite grain boundaries. By doping the monoamine porphyrins (MPs, M = Co, Ni, Cu, Zn, or H) into perovskite films, MPs self-assemble into supramolecules at grain boundaries. Organic cations in perovskites protonate MPs in supramolecules to form ammonium porphyrins bound on the perovskite grain surface, to passivate defects and extract holes from the perovskite lattice. Periodic polarons in supramolecules (especially NiP-supramolecule) promote the transport of extracted holes across boundaries, reducing nonradiative carrier recombination. The NiP-doped PSCs reveal a certified efficiency of 22.1% for an active area of 1.0 cm 2 with the remarkably improved open-circuit voltage and fill factor. The unencapsulated device retained over 80% initial performance under AM 1.5G solar light continuous illumination or heating at 85 °C over 3000 h.

In this paper, we study reinforcement learning (RL) algorithms to solve real-world decision problems with the objective of maximizing the long-term reward as well as satisfying cumulative constraints. We propose a novel first-order policy optimization method, Interior-point Policy Optimization (IPO), which augments the objective with logarithmic barrier functions, inspired by the interior-point method. Our proposed method is easy to implement with performance guarantees and can handle general types of cumulative multi-constraint settings. We conduct extensive evaluations to compare our approach with state-of-the-art baselines. Our algorithm outperforms the baseline algorithms, in terms of reward maximization and constraint satisfaction.

Accurate interface engineering can effectively inhibit iodide ion migration, thereby improving the stability and photovoltaic performance of perovskite solar cells (PvSCs). The time-of-flight secondary-ion mass spectrometry reveals that in an aged n-i-p-type PvSC, the iodide ions will move toward the rear side and enter the FTO cathode. In this regard, the authors describe a simple thermal evaporation strategy for introducing an NdCl 3 interface layer (NdCl 3 -IL) at the rear interface of perovskites to interdict the iodine ion migration pathway, leading to reduced trap densities throughout the whole perovskite region. As a result, a boosted open-circuit voltage (V OC ) is achieved, resulting in power conversion efficiency (PCE) up to 22.16% with negligible hysteresis. The NdCl 3 -IL also enhances the device stability, maintaining 83% of initial PCE after the maximum-power-point tracking test for 100 h. More encouragingly, a certified PCE of 21.68% is demonstrated on a large-area (1 cm 2 ) device with combined 2D/3D passivation strategies.

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